import com.sun.scenario.effect.impl.sw.sse.SSEBlend_SRC_OUTPeer;

import java.io.*;
import java.lang.reflect.Array;
import java.math.BigInteger;
import java.util.*;

public class Main {
    private static Scanner sc;
    private static Printer pr;
    static boolean []visited;
    static int []color;
    static int []pow=new int[(int)3e5+1];
    static int []count;
    static boolean check=true;
    static boolean checkBip=true;
    static ArrayList<Integer>[]list;
    private static long aLong=(long)(Math.pow(10,9)+7);
    static final long div=998244353;
    static  int answer=0;
    static int[]countSubTree;
    static int[]colorNode;
    static int ind=-1,countAns=0;
    static ArrayList<Integer>ans=new ArrayList<>();
    private static void solve() throws IOException {
        int t=sc.nextInt();
        while (t-->0){
            int n=sc.nextInt(),m=sc.nextInt();
            list=new ArrayList[n+1];
            visited=new boolean[n+1];
            for (int i=1;i<=n;i++)list[i]=new ArrayList<>();
            for (int i=1;i<=m;i++){
                int a=sc.nextInt(),b=sc.nextInt();
                list[a].add(b);
                list[b].add(a);
            }
            ArrayList<Integer>list1=new ArrayList<>();
            visited[1]=true;
            dfss(1,list1,1);
            TreeSet<Integer>set=new TreeSet<>();
            set.addAll(list1);
                /*for (int s:set){
                    boolean b=true;
                    for (int v:list[s]){
                        if (set.contains(v)){
                            node=s;
                            b=false;
                            break;
                        }
                    }
                    if (!b)break;
                }
                System.out.println(set.size()-1);
                for (int s:set){
                    if (s==node)continue;
                    System.out.print(s+" ");
                }
                System.out.println();*/
            ArrayList<Integer>arrayList=new ArrayList<>();
            while (!set.isEmpty()){
                boolean b=true;
                int node=set.pollFirst();
                for (int v:list[node]){
                    if (set.contains(v)){
                        b=false;
                        break;
                    }
                }
                if (b)arrayList.add(node);
            }
            System.out.println(arrayList.size());
            for (int s:arrayList) System.out.print(s+" ");
            System.out.println();
            //System.out.println("arr:"+arrayList);
            //System.out.println("list:"+list1);
        }

    }
    public static void dfss(int src,ArrayList<Integer>integers,int len){
        if (len%2==1)integers.add(src);
        for (int v:list[src]){
            if (!visited[v]){
                visited[v]=true;
                dfss(v,integers,len+1);
            }
        }
    }
    public static void dfsTask(int src,int par){
        boolean b=true;
        for (int v:list[src]){
            if (v!=par){
                System.out.println("v:"+v);
                if (colorNode[v]!=colorNode[1]){
                    b=false;
                    ind=v;
                    countAns++;
                    dfsTask(v,src);
                }
            }
        }
        System.out.println("ind:"+ind);
        if (b&&ind==par){
            System.out.println("src:"+src);
            ind=par;
            countAns--;
        }
    }
    public static class pairTask{
        long val;
        int ind;
        public pairTask(long  x, int  y) {
            this.val = x;
            this.ind = y;
        }
    }
    public static void subTree(int src,int parent){
        countSubTree[src]=1;
        for (int v:list[src]){
            if (v==parent)
                continue;
            subTree(v,src);
            countSubTree[src]+=countSubTree[v];
        }
    }
    public static boolean prime(long src){
        for (int i=2;i*i<=src;i++){
            if (src%i==0)
                return false;
        }
        return true;
    }
    public static void bfsColor(int src){
        Queue<Integer>queue = new ArrayDeque<>();
        queue.add(src);
        while (!queue.isEmpty()){
            boolean b=false;
            int vertex=-1,p=-1;
            int poll=queue.remove();
            for (int v:list[poll]){
                if (color [v]==0){
                    vertex=v;
                    break;
                }
            }
            for (int v:list[poll]){
                if (color [v]!=0&&v!=vertex){
                    p=v;
                    break;
                }
            }
            for (int v:list[p]){
                if (color [v]!=0){
                    color[vertex]=color[v];
                    b=true;
                    break;
                }
            }
            if (!b){
                color[vertex]=color[poll]+1;
            }
        }
    }
    static int add(int a,int b ){
        if (a+b>=div)
            return (int)(a+b-div);
        return (int)a+b;
    }
    public static int isBipartite(ArrayList<Integer>[]list,int src){
        color[src]=0;
        Queue<Integer>queue=new LinkedList<>();
        int []ans={0,0};
        queue.add(src);
        while (!queue.isEmpty()){
            ans[color[src=queue.poll()]]++;
            for (int v:list[src]){
                if (color[v]==-1){
                    queue.add(v);
                    color[v]=color[src]^1;
                }else if (color[v]==color[src])
                    check=false;
            }
        }
        return add(pow[ans[0]],pow[ans[1]]);
    }
    public static int powerMod(long b, long e){
        long ans=1;
        while (e-->0){
            ans=ans*b%div;
        }
        return (int)ans;
    }
    public static int dfs(int s){
        int ans=1;
        visited[s]=true;
        for (int k:list[s]){
            if (!visited[k]){
                ans+=dfs(k);
            }
        }
        return ans;
    }
    public static int[] radixSort(int[] f) {
        int[] to = new int[f.length];
        {
            int[] b = new int[65537];
            for (int i = 0; i < f.length; i++) b[1 + (f[i] & 0xffff)]++;
            for (int i = 1; i <= 65536; i++) b[i] += b[i - 1];
            for (int i = 0; i < f.length; i++) to[b[f[i] & 0xffff]++] = f[i];
            int[] d = f;
            f = to;
            to = d;
        }
        {
            int[] b = new int[65537];
            for (int i = 0; i < f.length; i++) b[1 + (f[i] >>> 16)]++;
            for (int i = 1; i <= 65536; i++) b[i] += b[i - 1];
            for (int i = 0; i < f.length; i++) to[b[f[i] >>> 16]++] = f[i];
            int[] d = f;
            f = to;
            to = d;
        }
        return f;
    }
    public static long []primeFactor(int n){
        long []prime=new long[n+1];
        prime[1]=1;
        for (int i=2;i<=n;i++)
            prime[i]=((i&1)==0)?2:i;
        for (int i=3;i*i<=n;i++){
            if (prime[i]==i){
                for (int j=i*i;j<=n;j+=i){
                    if (prime[j]==j)
                        prime[j]=i;
                }
            }
        }
        return prime;
    }
    public static StringBuilder binaryradix(long number){
        StringBuilder builder=new StringBuilder();
        long remainder;
        while (number!=0) {
            remainder = number % 2;
            number >>= 1;
            builder.append(remainder);
        }
        builder.reverse();
        return builder;
    }
    public static int binarySearch(long[] a, int index,long target) {
            int l = index;
            int h = a.length - 1;
            while (l<=h) {
                int med = l + (h-l)/2;
                if(a[med] - target <= target) {
                    l = med + 1;
                }
                else h = med  - 1;
            }
            return h;
    }
    public static int val(char c){
        return c-'0';
    }
    public static long gcd(long a,long b) {
        if (a == 0) return b;
        return gcd(b % a, a);
    }
        private static class Pair implements Comparable<Pair> {
            long x;
            long y;

            Pair() {
                this.x = 0;
                this.y = 0;
            }

            Pair(long x, long y) {
                this.x = x;
                this.y = y;
            }

            @Override
            public boolean equals(Object obj) {
                if (this == obj) {
                    return true;
                }
                if (obj == null) return false;
                Pair other = (Pair) obj;
                if (this.x == other.x && this.y == other.y) {
                    return true;
                }
                return false;
            }

            @Override
            public int compareTo(Pair other) {
                if (this.x != other.x) return Long.compare(this.x, other.x);
                return Long.compare(this.y*other.x, this.x*other.y);
            }
    }

    public static void main(String[] args) throws IOException {
        sc = new Scanner(System.in);
        pr = new Printer(System.out);
        solve();

        pr.close();
       // sc.close();
    }
    private static class Scanner {
        BufferedReader br;

        Scanner (InputStream in) {
            br = new BufferedReader(new InputStreamReader(in));
        }

        private boolean isPrintable(int ch) {
            return ch >= '!' && ch <= '~';
        }

        private boolean isCRLF(int ch) {
            return ch == '\n' || ch == '\r' || ch == -1;
        }

        private int nextPrintable() {
            try {
                int ch;
                while (!isPrintable(ch = br.read())) {
                    if (ch == -1) {
                        throw new NoSuchElementException();
                    }
                }

                return ch;
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        String next() {
            try {
                int ch = nextPrintable();
                StringBuilder sb = new StringBuilder();
                do {
                    sb.appendCodePoint(ch);
                } while (isPrintable(ch = br.read()));

                return sb.toString();
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        int nextInt() {
            try {
                // parseInt from Integer.parseInt()
                boolean negative = false;
                int res = 0;
                int limit = -Integer.MAX_VALUE;
                int radix = 10;

                int fc = nextPrintable();
                if (fc < '0') {
                    if (fc == '-') {
                        negative = true;
                        limit = Integer.MIN_VALUE;
                    } else if (fc != '+') {
                        throw new NumberFormatException();
                    }
                    fc = br.read();
                }
                int multmin = limit / radix;

                int ch = fc;
                do {
                    int digit = ch - '0';
                    if (digit < 0 || digit >= radix) {
                        throw new NumberFormatException();
                    }
                    if (res < multmin) {
                        throw new NumberFormatException();
                    }
                    res *= radix;
                    if (res < limit + digit) {
                        throw new NumberFormatException();
                    }
                    res -= digit;

                } while (isPrintable(ch = br.read()));

                return negative ? res : -res;
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        long nextLong() {
            try {
                // parseLong from Long.parseLong()
                boolean negative = false;
                long res = 0;
                long limit = -Long.MAX_VALUE;
                int radix = 10;

                int fc = nextPrintable();
                if (fc < '0') {
                    if (fc == '-') {
                        negative = true;
                        limit = Long.MIN_VALUE;
                    } else if (fc != '+') {
                        throw new NumberFormatException();
                    }
                    fc = br.read();
                }
                long multmin = limit / radix;

                int ch = fc;
                do {
                    int digit = ch - '0';
                    if (digit < 0 || digit >= radix) {
                        throw new NumberFormatException();
                    }
                    if (res < multmin) {
                        throw new NumberFormatException();
                    }
                    res *= radix;
                    if (res < limit + digit) {
                        throw new NumberFormatException();
                    }
                    res -= digit;

                } while (isPrintable(ch = br.read()));

                return negative ? res : -res;
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        float nextFloat() {
            return Float.parseFloat(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            try {
                int ch;
                while (isCRLF(ch = br.read())) {
                    if (ch == -1) {
                        throw new NoSuchElementException();
                    }
                }
                StringBuilder sb = new StringBuilder();
                do {
                    sb.appendCodePoint(ch);
                } while (!isCRLF(ch = br.read()));

                return sb.toString();
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        void close() {
            try {
                br.close();
            } catch (IOException e) {
//				throw new NoSuchElementException();
            }
        }
    }
    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }

    static class List {
        String Word;
        int length;

        List(String Word, int length) {
            this.Word = Word;
            this.length = length;
        }
    }
    private static class Printer extends PrintWriter {
        Printer(PrintStream out) {
            super(out);
        }
    }
}


import com.sun.scenario.effect.impl.sw.sse.SSEBlend_SRC_OUTPeer;

import java.io.*;
import java.lang.reflect.Array;
import java.math.BigInteger;
import java.util.*;

public class Main {
    private static Scanner sc;
    private static Printer pr;
    static boolean []visited;
    static int []color;
    static int []pow=new int[(int)3e5+1];
    static int []count;
    static boolean check=true;
    static boolean checkBip=true;
    static ArrayList<Integer>[]list;
    private static long aLong=(long)(Math.pow(10,9)+7);
    static final long div=998244353;
    static  int answer=0;
    static int[]countSubTree;
    static int[]colorNode;
    static int ind=-1,countAns=0;
    static ArrayList<Integer>ans=new ArrayList<>();
    private static void solve() throws IOException {
        int t=sc.nextInt();
        while (t-->0){
            int n=sc.nextInt(),m=sc.nextInt();
            list=new ArrayList[n+1];
            visited=new boolean[n+1];
            TreeSet<pairTask>set=new TreeSet<>(new Comparator<pairTask>() {
                @Override
                public int compare(pairTask o1, pairTask o2) {
                    if (o1.size<o2.size)return 1;
                    else if (o1.size>o2.size)return -1;
                    return 0;
                }
            });
            for (int i=1;i<=n;i++) list[i]=new ArrayList<>();
            for (int i=1;i<=m;i++){
                int a=sc.nextInt(),b=sc.nextInt();
                list[a].add(b);
                list[b].add(a);
            }
            for (int i=1;i<=n;i++)set.add(new pairTask(i,list[i].size()));
            TreeSet<Integer>ansList=new TreeSet<>();
            while (!set.isEmpty()){
                pairTask task=set.pollFirst();
                if (!visited[task.val]) {
                    ansList.add(task.val);
                    visited[task.val] = true;
                    for (int v : list[task.val]) {
                        if (!visited[v]) visited[v] = true;
                    }
                }
            }
            //System.out.println("ansList:"+ansList);
            if (ansList.size()<=n/2){
                System.out.println(ansList.size());
                for (int s:ansList) System.out.print(s+" ");
                System.out.println();
            }else {
                ArrayList<Integer>ans1=new ArrayList<>();
                for (int i=1;i<=n;i++){
                    if (!ansList.contains(i))ans1.add(i);
                }
                System.out.println(ans1.size());
                for (int i:ans1) System.out.print(i+" ");
                System.out.println();
            }
        }

    }
    public static void dfsTask(int src,int par){
        boolean b=true;
        for (int v:list[src]){
            if (v!=par){
                System.out.println("v:"+v);
                if (colorNode[v]!=colorNode[1]){
                    b=false;
                    ind=v;
                    countAns++;
                    dfsTask(v,src);
                }
            }
        }
        System.out.println("ind:"+ind);
        if (b&&ind==par){
            System.out.println("src:"+src);
            ind=par;
            countAns--;
        }
    }
    public static class pairTask{
        int  val;
        int size;
        public pairTask(int   x, int  y) {
            this.val = x;
            this.size = y;
        }
    }
    public static void subTree(int src,int parent){
        countSubTree[src]=1;
        for (int v:list[src]){
            if (v==parent)
                continue;
            subTree(v,src);
            countSubTree[src]+=countSubTree[v];
        }
    }
    public static boolean prime(long src){
        for (int i=2;i*i<=src;i++){
            if (src%i==0)
                return false;
        }
        return true;
    }
    public static void bfsColor(int src){
        Queue<Integer>queue = new ArrayDeque<>();
        queue.add(src);
        while (!queue.isEmpty()){
            boolean b=false;
            int vertex=-1,p=-1;
            int poll=queue.remove();
            for (int v:list[poll]){
                if (color [v]==0){
                    vertex=v;
                    break;
                }
            }
            for (int v:list[poll]){
                if (color [v]!=0&&v!=vertex){
                    p=v;
                    break;
                }
            }
            for (int v:list[p]){
                if (color [v]!=0){
                    color[vertex]=color[v];
                    b=true;
                    break;
                }
            }
            if (!b){
                color[vertex]=color[poll]+1;
            }
        }
    }
    static int add(int a,int b ){
        if (a+b>=div)
            return (int)(a+b-div);
        return (int)a+b;
    }
    public static int isBipartite(ArrayList<Integer>[]list,int src){
        color[src]=0;
        Queue<Integer>queue=new LinkedList<>();
        int []ans={0,0};
        queue.add(src);
        while (!queue.isEmpty()){
            ans[color[src=queue.poll()]]++;
            for (int v:list[src]){
                if (color[v]==-1){
                    queue.add(v);
                    color[v]=color[src]^1;
                }else if (color[v]==color[src])
                    check=false;
            }
        }
        return add(pow[ans[0]],pow[ans[1]]);
    }
    public static int powerMod(long b, long e){
        long ans=1;
        while (e-->0){
            ans=ans*b%div;
        }
        return (int)ans;
    }
    public static int dfs(int s){
        int ans=1;
        visited[s]=true;
        for (int k:list[s]){
            if (!visited[k]){
                ans+=dfs(k);
            }
        }
        return ans;
    }
    public static int[] radixSort(int[] f) {
        int[] to = new int[f.length];
        {
            int[] b = new int[65537];
            for (int i = 0; i < f.length; i++) b[1 + (f[i] & 0xffff)]++;
            for (int i = 1; i <= 65536; i++) b[i] += b[i - 1];
            for (int i = 0; i < f.length; i++) to[b[f[i] & 0xffff]++] = f[i];
            int[] d = f;
            f = to;
            to = d;
        }
        {
            int[] b = new int[65537];
            for (int i = 0; i < f.length; i++) b[1 + (f[i] >>> 16)]++;
            for (int i = 1; i <= 65536; i++) b[i] += b[i - 1];
            for (int i = 0; i < f.length; i++) to[b[f[i] >>> 16]++] = f[i];
            int[] d = f;
            f = to;
            to = d;
        }
        return f;
    }
    public static long []primeFactor(int n){
        long []prime=new long[n+1];
        prime[1]=1;
        for (int i=2;i<=n;i++)
            prime[i]=((i&1)==0)?2:i;
        for (int i=3;i*i<=n;i++){
            if (prime[i]==i){
                for (int j=i*i;j<=n;j+=i){
                    if (prime[j]==j)
                        prime[j]=i;
                }
            }
        }
        return prime;
    }
    public static StringBuilder binaryradix(long number){
        StringBuilder builder=new StringBuilder();
        long remainder;
        while (number!=0) {
            remainder = number % 2;
            number >>= 1;
            builder.append(remainder);
        }
        builder.reverse();
        return builder;
    }
    public static int binarySearch(long[] a, int index,long target) {
            int l = index;
            int h = a.length - 1;
            while (l<=h) {
                int med = l + (h-l)/2;
                if(a[med] - target <= target) {
                    l = med + 1;
                }
                else h = med  - 1;
            }
            return h;
    }
    public static int val(char c){
        return c-'0';
    }
    public static long gcd(long a,long b) {
        if (a == 0) return b;
        return gcd(b % a, a);
    }
        private static class Pair implements Comparable<Pair> {
            long x;
            long y;

            Pair() {
                this.x = 0;
                this.y = 0;
            }

            Pair(long x, long y) {
                this.x = x;
                this.y = y;
            }

            @Override
            public boolean equals(Object obj) {
                if (this == obj) {
                    return true;
                }
                if (obj == null) return false;
                Pair other = (Pair) obj;
                if (this.x == other.x && this.y == other.y) {
                    return true;
                }
                return false;
            }

            @Override
            public int compareTo(Pair other) {
                if (this.x != other.x) return Long.compare(this.x, other.x);
                return Long.compare(this.y*other.x, this.x*other.y);
            }
    }

    public static void main(String[] args) throws IOException {
        sc = new Scanner(System.in);
        pr = new Printer(System.out);
        solve();

        pr.close();
       // sc.close();
    }
    private static class Scanner {
        BufferedReader br;

        Scanner (InputStream in) {
            br = new BufferedReader(new InputStreamReader(in));
        }

        private boolean isPrintable(int ch) {
            return ch >= '!' && ch <= '~';
        }

        private boolean isCRLF(int ch) {
            return ch == '\n' || ch == '\r' || ch == -1;
        }

        private int nextPrintable() {
            try {
                int ch;
                while (!isPrintable(ch = br.read())) {
                    if (ch == -1) {
                        throw new NoSuchElementException();
                    }
                }

                return ch;
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        String next() {
            try {
                int ch = nextPrintable();
                StringBuilder sb = new StringBuilder();
                do {
                    sb.appendCodePoint(ch);
                } while (isPrintable(ch = br.read()));

                return sb.toString();
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        int nextInt() {
            try {
                // parseInt from Integer.parseInt()
                boolean negative = false;
                int res = 0;
                int limit = -Integer.MAX_VALUE;
                int radix = 10;

                int fc = nextPrintable();
                if (fc < '0') {
                    if (fc == '-') {
                        negative = true;
                        limit = Integer.MIN_VALUE;
                    } else if (fc != '+') {
                        throw new NumberFormatException();
                    }
                    fc = br.read();
                }
                int multmin = limit / radix;

                int ch = fc;
                do {
                    int digit = ch - '0';
                    if (digit < 0 || digit >= radix) {
                        throw new NumberFormatException();
                    }
                    if (res < multmin) {
                        throw new NumberFormatException();
                    }
                    res *= radix;
                    if (res < limit + digit) {
                        throw new NumberFormatException();
                    }
                    res -= digit;

                } while (isPrintable(ch = br.read()));

                return negative ? res : -res;
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        long nextLong() {
            try {
                // parseLong from Long.parseLong()
                boolean negative = false;
                long res = 0;
                long limit = -Long.MAX_VALUE;
                int radix = 10;

                int fc = nextPrintable();
                if (fc < '0') {
                    if (fc == '-') {
                        negative = true;
                        limit = Long.MIN_VALUE;
                    } else if (fc != '+') {
                        throw new NumberFormatException();
                    }
                    fc = br.read();
                }
                long multmin = limit / radix;

                int ch = fc;
                do {
                    int digit = ch - '0';
                    if (digit < 0 || digit >= radix) {
                        throw new NumberFormatException();
                    }
                    if (res < multmin) {
                        throw new NumberFormatException();
                    }
                    res *= radix;
                    if (res < limit + digit) {
                        throw new NumberFormatException();
                    }
                    res -= digit;

                } while (isPrintable(ch = br.read()));

                return negative ? res : -res;
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        float nextFloat() {
            return Float.parseFloat(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            try {
                int ch;
                while (isCRLF(ch = br.read())) {
                    if (ch == -1) {
                        throw new NoSuchElementException();
                    }
                }
                StringBuilder sb = new StringBuilder();
                do {
                    sb.appendCodePoint(ch);
                } while (!isCRLF(ch = br.read()));

                return sb.toString();
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        void close() {
            try {
                br.close();
            } catch (IOException e) {
//				throw new NoSuchElementException();
            }
        }
    }
    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }

    static class List {
        String Word;
        int length;

        List(String Word, int length) {
            this.Word = Word;
            this.length = length;
        }
    }
    private static class Printer extends PrintWriter {
        Printer(PrintStream out) {
            super(out);
        }
    }
}


import com.sun.scenario.effect.impl.sw.sse.SSEBlend_SRC_OUTPeer;

import java.awt.image.VolatileImage;
import java.io.*;
import java.lang.reflect.Array;
import java.math.BigInteger;
import java.util.*;

public class Main {
    private static Scanner sc;
    private static Printer pr;
    static boolean []visited;
    static int []color;
    static int []pow=new int[(int)3e5+1];
    static int []count;
    static boolean check=true;
    static boolean checkBip=true;
    static ArrayList<Integer>[]list;
    private static long aLong=(long)(Math.pow(10,9)+7);
    static final long div=998244353;
    static  int answer=0;
    static int[]countSubTree;
    static int[]colorNode;
    private static void solve() throws IOException {
        int t=sc.nextInt();
        StringBuilder builder=new StringBuilder();
        while (t-->0){
            int n = sc.nextInt();
            int m = sc.nextInt();
            int[] c = new int[n+1];
            int count = 0;
            for(int j=0;j<m;++j){
                int a = sc.nextInt();
                int b = sc.nextInt();
                if(c[a]>0 && c[b]>0)
                    continue;
                if(c[a] == 0 && c[b] == 0){
                    count++;
                    c[b] = 1;
                    c[a] = 2;
                }
                if(c[a] == 0){
                    count += (c[b] == 2) ? 1 : 0;
                    c[a] = (c[b] == 1) ? 2 : 1;
                }
                if(c[b] == 0){
                    count += (c[a] == 2) ? 1 : 0;
                    c[b] = (c[a] == 1) ? 2 : 1;
                }
            }
            if(count <= n/2){
                builder.append(count + "\n");
                printSolve(builder,c,n,1);
            }else{
                builder.append(n-count + "\n");
                printSolve(builder,c,n,2);
            }
        }
        pr.println(builder);
    }
    public static void printSolve(StringBuilder str, int[] colors, int n,int color){
        for(int i = 1;i<=n;++i)
            if(colors[i] == color)
                str.append(i + " ");
        str.append('\n');
    }
    public static class pairTask{
        int  val;
        int size;
        public pairTask(int   x, int  y) {
            this.val = x;
            this.size = y;
        }
    }
    public static void subTree(int src,int parent){
        countSubTree[src]=1;
        for (int v:list[src]){
            if (v==parent)
                continue;
            subTree(v,src);
            countSubTree[src]+=countSubTree[v];
        }
    }
    public static boolean prime(long src){
        for (int i=2;i*i<=src;i++){
            if (src%i==0)
                return false;
        }
        return true;
    }
    public static void bfsColor(int src){
        Queue<Integer>queue = new ArrayDeque<>();
        queue.add(src);
        while (!queue.isEmpty()){
            boolean b=false;
            int vertex=-1,p=-1;
            int poll=queue.remove();
            for (int v:list[poll]){
                if (color [v]==0){
                    vertex=v;
                    break;
                }
            }
            for (int v:list[poll]){
                if (color [v]!=0&&v!=vertex){
                    p=v;
                    break;
                }
            }
            for (int v:list[p]){
                if (color [v]!=0){
                    color[vertex]=color[v];
                    b=true;
                    break;
                }
            }
            if (!b){
                color[vertex]=color[poll]+1;
            }
        }
    }
    static int add(int a,int b ){
        if (a+b>=div)
            return (int)(a+b-div);
        return (int)a+b;
    }
    public static int isBipartite(ArrayList<Integer>[]list,int src){
        color[src]=0;
        Queue<Integer>queue=new LinkedList<>();
        int []ans={0,0};
        queue.add(src);
        while (!queue.isEmpty()){
            ans[color[src=queue.poll()]]++;
            for (int v:list[src]){
                if (color[v]==-1){
                    queue.add(v);
                    color[v]=color[src]^1;
                }else if (color[v]==color[src])
                    check=false;
            }
        }
        return add(pow[ans[0]],pow[ans[1]]);
    }
    public static int powerMod(long b, long e){
        long ans=1;
        while (e-->0){
            ans=ans*b%div;
        }
        return (int)ans;
    }
    public static int dfs(int s){
        int ans=1;
        visited[s]=true;
        for (int k:list[s]){
            if (!visited[k]){
                ans+=dfs(k);
            }
        }
        return ans;
    }
    public static int[] radixSort(int[] f) {
        int[] to = new int[f.length];
        {
            int[] b = new int[65537];
            for (int i = 0; i < f.length; i++) b[1 + (f[i] & 0xffff)]++;
            for (int i = 1; i <= 65536; i++) b[i] += b[i - 1];
            for (int i = 0; i < f.length; i++) to[b[f[i] & 0xffff]++] = f[i];
            int[] d = f;
            f = to;
            to = d;
        }
        {
            int[] b = new int[65537];
            for (int i = 0; i < f.length; i++) b[1 + (f[i] >>> 16)]++;
            for (int i = 1; i <= 65536; i++) b[i] += b[i - 1];
            for (int i = 0; i < f.length; i++) to[b[f[i] >>> 16]++] = f[i];
            int[] d = f;
            f = to;
            to = d;
        }
        return f;
    }
    public static long []primeFactor(int n){
        long []prime=new long[n+1];
        prime[1]=1;
        for (int i=2;i<=n;i++)
            prime[i]=((i&1)==0)?2:i;
        for (int i=3;i*i<=n;i++){
            if (prime[i]==i){
                for (int j=i*i;j<=n;j+=i){
                    if (prime[j]==j)
                        prime[j]=i;
                }
            }
        }
        return prime;
    }
    public static StringBuilder binaryradix(long number){
        StringBuilder builder=new StringBuilder();
        long remainder;
        while (number!=0) {
            remainder = number % 2;
            number >>= 1;
            builder.append(remainder);
        }
        builder.reverse();
        return builder;
    }
    public static int binarySearch(long[] a, int index,long target) {
            int l = index;
            int h = a.length - 1;
            while (l<=h) {
                int med = l + (h-l)/2;
                if(a[med] - target <= target) {
                    l = med + 1;
                }
                else h = med  - 1;
            }
            return h;
    }
    public static int val(char c){
        return c-'0';
    }
    public static long gcd(long a,long b) {
        if (a == 0) return b;
        return gcd(b % a, a);
    }
        private static class Pair implements Comparable<Pair> {
            long x;
            long y;

            Pair() {
                this.x = 0;
                this.y = 0;
            }

            Pair(long x, long y) {
                this.x = x;
                this.y = y;
            }

            @Override
            public boolean equals(Object obj) {
                if (this == obj) {
                    return true;
                }
                if (obj == null) return false;
                Pair other = (Pair) obj;
                if (this.x == other.x && this.y == other.y) {
                    return true;
                }
                return false;
            }

            @Override
            public int compareTo(Pair other) {
                if (this.x != other.x) return Long.compare(this.x, other.x);
                return Long.compare(this.y*other.x, this.x*other.y);
            }
    }

    public static void main(String[] args) throws IOException {
        sc = new Scanner(System.in);
        pr = new Printer(System.out);
        solve();

        pr.close();
       // sc.close();
    }
    private static class Scanner {
        BufferedReader br;

        Scanner (InputStream in) {
            br = new BufferedReader(new InputStreamReader(in));
        }

        private boolean isPrintable(int ch) {
            return ch >= '!' && ch <= '~';
        }

        private boolean isCRLF(int ch) {
            return ch == '\n' || ch == '\r' || ch == -1;
        }

        private int nextPrintable() {
            try {
                int ch;
                while (!isPrintable(ch = br.read())) {
                    if (ch == -1) {
                        throw new NoSuchElementException();
                    }
                }

                return ch;
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        String next() {
            try {
                int ch = nextPrintable();
                StringBuilder sb = new StringBuilder();
                do {
                    sb.appendCodePoint(ch);
                } while (isPrintable(ch = br.read()));

                return sb.toString();
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        int nextInt() {
            try {
                // parseInt from Integer.parseInt()
                boolean negative = false;
                int res = 0;
                int limit = -Integer.MAX_VALUE;
                int radix = 10;

                int fc = nextPrintable();
                if (fc < '0') {
                    if (fc == '-') {
                        negative = true;
                        limit = Integer.MIN_VALUE;
                    } else if (fc != '+') {
                        throw new NumberFormatException();
                    }
                    fc = br.read();
                }
                int multmin = limit / radix;

                int ch = fc;
                do {
                    int digit = ch - '0';
                    if (digit < 0 || digit >= radix) {
                        throw new NumberFormatException();
                    }
                    if (res < multmin) {
                        throw new NumberFormatException();
                    }
                    res *= radix;
                    if (res < limit + digit) {
                        throw new NumberFormatException();
                    }
                    res -= digit;

                } while (isPrintable(ch = br.read()));

                return negative ? res : -res;
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        long nextLong() {
            try {
                // parseLong from Long.parseLong()
                boolean negative = false;
                long res = 0;
                long limit = -Long.MAX_VALUE;
                int radix = 10;

                int fc = nextPrintable();
                if (fc < '0') {
                    if (fc == '-') {
                        negative = true;
                        limit = Long.MIN_VALUE;
                    } else if (fc != '+') {
                        throw new NumberFormatException();
                    }
                    fc = br.read();
                }
                long multmin = limit / radix;

                int ch = fc;
                do {
                    int digit = ch - '0';
                    if (digit < 0 || digit >= radix) {
                        throw new NumberFormatException();
                    }
                    if (res < multmin) {
                        throw new NumberFormatException();
                    }
                    res *= radix;
                    if (res < limit + digit) {
                        throw new NumberFormatException();
                    }
                    res -= digit;

                } while (isPrintable(ch = br.read()));

                return negative ? res : -res;
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        float nextFloat() {
            return Float.parseFloat(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            try {
                int ch;
                while (isCRLF(ch = br.read())) {
                    if (ch == -1) {
                        throw new NoSuchElementException();
                    }
                }
                StringBuilder sb = new StringBuilder();
                do {
                    sb.appendCodePoint(ch);
                } while (!isCRLF(ch = br.read()));

                return sb.toString();
            } catch (IOException e) {
                throw new NoSuchElementException();
            }
        }

        void close() {
            try {
                br.close();
            } catch (IOException e) {
//				throw new NoSuchElementException();
            }
        }
    }
    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }

    static class List {
        String Word;
        int length;

        List(String Word, int length) {
            this.Word = Word;
            this.length = length;
        }
    }
    private static class Printer extends PrintWriter {
        Printer(PrintStream out) {
            super(out);
        }
    }
}


import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.io.BufferedWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Osmanys Alonso (osmanys@gmail.com)
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        TaskE solver = new TaskE();
        int testCount = Integer.parseInt(in.next());
        for (int i = 1; i <= testCount; i++)
            solver.solve(i, in, out);
        out.close();
    }

    static class TaskE {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
            int n = in.readInt();
            int u, v, m = in.readInt();
            Graph g = new Graph(n);
            for (int i = 0; i < m; i++) {
                u = in.readInt() - 1;
                v = in.readInt() - 1;
                g.addSimpleEdge(u, v);
                g.addSimpleEdge(v, u);
            }
            boolean selected[] = new boolean[n];
            boolean visited[] = new boolean[n];
            int r = go(g, 0, visited, true, selected);
            out.printLine(r);
            for (int i = 0; i < n; i++) {
                if (selected[i])
                    out.print((i + 1) + " ");
            }
            out.printLine();
        }

        private int go(Graph g, int v, boolean visited[], boolean select, boolean selected[]) {
            visited[v] = true;
            int next;
            Edge edge;
            boolean found = false;
            for (int e = g.firstOutbound(v); e != -1; e = g.nextOutbound(e)) {
                edge = g.edge(e);
                next = edge.getDestination();
                if (selected[next]) {
                    found = true;
                    break;
                }
            }
            int r = 0;
            if (select && !found) {
                selected[v] = true;
                r++;
            }
            for (int e = g.firstOutbound(v); e != -1; e = g.nextOutbound(e)) {
                edge = g.edge(e);
                next = edge.getDestination();
                if (!visited[next])
                    r += go(g, next, visited, !select || found, selected);
            }
            return r;
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public int readInt() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public String readString() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                if (Character.isValidCodePoint(c)) {
                    res.appendCodePoint(c);
                }
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public String next() {
            return readString();
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void print(Object... objects) {
            for (int i = 0; i < objects.length; i++) {
                if (i != 0) {
                    writer.print(' ');
                }
                writer.print(objects[i]);
            }
        }

        public void printLine() {
            writer.println();
        }

        public void close() {
            writer.close();
        }

        public void printLine(int i) {
            writer.println(i);
        }

    }

    static interface Edge {
        public int getDestination();

    }

    static class Graph {
        public static final int REMOVED_BIT = 0;
        protected int vertexCount;
        protected int edgeCount;
        private int[] firstOutbound;
        private int[] firstInbound;
        private Edge[] edges;
        private int[] nextInbound;
        private int[] nextOutbound;
        private int[] from;
        private int[] to;
        private long[] weight;
        public long[] capacity;
        private int[] reverseEdge;
        private int[] flags;

        public Graph(int vertexCount) {
            this(vertexCount, vertexCount);
        }

        public Graph(int vertexCount, int edgeCapacity) {
            this.vertexCount = vertexCount;
            firstOutbound = new int[vertexCount];
            Arrays.fill(firstOutbound, -1);

            from = new int[edgeCapacity];
            to = new int[edgeCapacity];
            nextOutbound = new int[edgeCapacity];
            flags = new int[edgeCapacity];
        }

        public int addEdge(int fromID, int toID, long weight, long capacity, int reverseEdge) {
            ensureEdgeCapacity(edgeCount + 1);
            if (firstOutbound[fromID] != -1) {
                nextOutbound[edgeCount] = firstOutbound[fromID];
            } else {
                nextOutbound[edgeCount] = -1;
            }
            firstOutbound[fromID] = edgeCount;
            if (firstInbound != null) {
                if (firstInbound[toID] != -1) {
                    nextInbound[edgeCount] = firstInbound[toID];
                } else {
                    nextInbound[edgeCount] = -1;
                }
                firstInbound[toID] = edgeCount;
            }
            this.from[edgeCount] = fromID;
            this.to[edgeCount] = toID;
            if (capacity != 0) {
                if (this.capacity == null) {
                    this.capacity = new long[from.length];
                }
                this.capacity[edgeCount] = capacity;
            }
            if (weight != 0) {
                if (this.weight == null) {
                    this.weight = new long[from.length];
                }
                this.weight[edgeCount] = weight;
            }
            if (reverseEdge != -1) {
                if (this.reverseEdge == null) {
                    this.reverseEdge = new int[from.length];
                    Arrays.fill(this.reverseEdge, 0, edgeCount, -1);
                }
                this.reverseEdge[edgeCount] = reverseEdge;
            }
            if (edges != null) {
                edges[edgeCount] = createEdge(edgeCount);
            }
            return edgeCount++;
        }

        protected final GraphEdge createEdge(int id) {
            return new GraphEdge(id);
        }

        public final int addFlowWeightedEdge(int from, int to, long weight, long capacity) {
            if (capacity == 0) {
                return addEdge(from, to, weight, 0, -1);
            } else {
                int lastEdgeCount = edgeCount;
                addEdge(to, from, -weight, 0, lastEdgeCount + entriesPerEdge());
                return addEdge(from, to, weight, capacity, lastEdgeCount);
            }
        }

        protected int entriesPerEdge() {
            return 1;
        }

        public final int addWeightedEdge(int from, int to, long weight) {
            return addFlowWeightedEdge(from, to, weight, 0);
        }

        public final int addSimpleEdge(int from, int to) {
            return addWeightedEdge(from, to, 0);
        }

        public final Edge edge(int id) {
            initEdges();
            return edges[id];
        }

        public final int firstOutbound(int vertex) {
            int id = firstOutbound[vertex];
            while (id != -1 && isRemoved(id)) {
                id = nextOutbound[id];
            }
            return id;
        }

        public final int nextOutbound(int id) {
            id = nextOutbound[id];
            while (id != -1 && isRemoved(id)) {
                id = nextOutbound[id];
            }
            return id;
        }

        public final int destination(int id) {
            return to[id];
        }

        protected final void initEdges() {
            if (edges == null) {
                edges = new Edge[from.length];
                for (int i = 0; i < edgeCount; i++) {
                    edges[i] = createEdge(i);
                }
            }
        }

        public final boolean flag(int id, int bit) {
            return (flags[id] >> bit & 1) != 0;
        }

        public final boolean isRemoved(int id) {
            return flag(id, REMOVED_BIT);
        }

        protected void ensureEdgeCapacity(int size) {
            if (from.length < size) {
                int newSize = Math.max(size, 2 * from.length);
                if (edges != null) {
                    edges = resize(edges, newSize);
                }
                from = resize(from, newSize);
                to = resize(to, newSize);
                nextOutbound = resize(nextOutbound, newSize);
                if (nextInbound != null) {
                    nextInbound = resize(nextInbound, newSize);
                }
                if (weight != null) {
                    weight = resize(weight, newSize);
                }
                if (capacity != null) {
                    capacity = resize(capacity, newSize);
                }
                if (reverseEdge != null) {
                    reverseEdge = resize(reverseEdge, newSize);
                }
                flags = resize(flags, newSize);
            }
        }

        protected final int[] resize(int[] array, int size) {
            int[] newArray = new int[size];
            System.arraycopy(array, 0, newArray, 0, array.length);
            return newArray;
        }

        private long[] resize(long[] array, int size) {
            long[] newArray = new long[size];
            System.arraycopy(array, 0, newArray, 0, array.length);
            return newArray;
        }

        private Edge[] resize(Edge[] array, int size) {
            Edge[] newArray = new Edge[size];
            System.arraycopy(array, 0, newArray, 0, array.length);
            return newArray;
        }

        protected class GraphEdge implements Edge {
            protected int id;

            protected GraphEdge(int id) {
                this.id = id;
            }

            public int getDestination() {
                return destination(id);
            }

        }

    }
}


import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.io.BufferedWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Osmanys Alonso (osmanys@gmail.com)
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        TaskE solver = new TaskE();
        int testCount = Integer.parseInt(in.next());
        for (int i = 1; i <= testCount; i++)
            solver.solve(i, in, out);
        out.close();
    }

    static class TaskE {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
            int n = in.readInt();
            int u, v, m = in.readInt();
            Graph g = new Graph(n);
            int cnt[] = new int[n];
            for (int i = 0; i < m; i++) {
                u = in.readInt() - 1;
                v = in.readInt() - 1;
                g.addSimpleEdge(u, v);
                g.addSimpleEdge(v, u);
                cnt[u]++;
                cnt[v]++;
            }
            boolean selected[] = new boolean[n];
            boolean visited[] = new boolean[n];
            int r = n;
            int max = 0, idx = 0;
            for (int i = 0; i < n; i++) {
                if (max < cnt[i]) {
                    max = cnt[i];
                    idx = i;
                }
            }
            while (idx < n && r > n / 2) {
                r = go(g, idx, visited, selected);
                idx++;
            }
            out.printLine(r);
            for (int i = 0; i < n; i++) {
                if (selected[i])
                    out.print((i + 1) + " ");
            }
            out.printLine();
        }

        private int go(Graph g, int v, boolean visited[], boolean selected[]) {
            visited[v] = true;
            int next;
            Edge edge;
            boolean found = false;
            for (int e = g.firstOutbound(v); e != -1; e = g.nextOutbound(e)) {
                edge = g.edge(e);
                next = edge.getDestination();
                if (selected[next]) {
                    found = true;
                    break;
                }
            }
            int r = 0;
            if (!found) {
                selected[v] = true;
                r++;
            }
            for (int e = g.firstOutbound(v); e != -1; e = g.nextOutbound(e)) {
                edge = g.edge(e);
                next = edge.getDestination();
                if (!visited[next])
                    r += go(g, next, visited, selected);
            }
            return r;
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public int readInt() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public String readString() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                if (Character.isValidCodePoint(c)) {
                    res.appendCodePoint(c);
                }
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public String next() {
            return readString();
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void print(Object... objects) {
            for (int i = 0; i < objects.length; i++) {
                if (i != 0) {
                    writer.print(' ');
                }
                writer.print(objects[i]);
            }
        }

        public void printLine() {
            writer.println();
        }

        public void close() {
            writer.close();
        }

        public void printLine(int i) {
            writer.println(i);
        }

    }

    static interface Edge {
        public int getDestination();

    }

    static class Graph {
        public static final int REMOVED_BIT = 0;
        protected int vertexCount;
        protected int edgeCount;
        private int[] firstOutbound;
        private int[] firstInbound;
        private Edge[] edges;
        private int[] nextInbound;
        private int[] nextOutbound;
        private int[] from;
        private int[] to;
        private long[] weight;
        public long[] capacity;
        private int[] reverseEdge;
        private int[] flags;

        public Graph(int vertexCount) {
            this(vertexCount, vertexCount);
        }

        public Graph(int vertexCount, int edgeCapacity) {
            this.vertexCount = vertexCount;
            firstOutbound = new int[vertexCount];
            Arrays.fill(firstOutbound, -1);

            from = new int[edgeCapacity];
            to = new int[edgeCapacity];
            nextOutbound = new int[edgeCapacity];
            flags = new int[edgeCapacity];
        }

        public int addEdge(int fromID, int toID, long weight, long capacity, int reverseEdge) {
            ensureEdgeCapacity(edgeCount + 1);
            if (firstOutbound[fromID] != -1) {
                nextOutbound[edgeCount] = firstOutbound[fromID];
            } else {
                nextOutbound[edgeCount] = -1;
            }
            firstOutbound[fromID] = edgeCount;
            if (firstInbound != null) {
                if (firstInbound[toID] != -1) {
                    nextInbound[edgeCount] = firstInbound[toID];
                } else {
                    nextInbound[edgeCount] = -1;
                }
                firstInbound[toID] = edgeCount;
            }
            this.from[edgeCount] = fromID;
            this.to[edgeCount] = toID;
            if (capacity != 0) {
                if (this.capacity == null) {
                    this.capacity = new long[from.length];
                }
                this.capacity[edgeCount] = capacity;
            }
            if (weight != 0) {
                if (this.weight == null) {
                    this.weight = new long[from.length];
                }
                this.weight[edgeCount] = weight;
            }
            if (reverseEdge != -1) {
                if (this.reverseEdge == null) {
                    this.reverseEdge = new int[from.length];
                    Arrays.fill(this.reverseEdge, 0, edgeCount, -1);
                }
                this.reverseEdge[edgeCount] = reverseEdge;
            }
            if (edges != null) {
                edges[edgeCount] = createEdge(edgeCount);
            }
            return edgeCount++;
        }

        protected final GraphEdge createEdge(int id) {
            return new GraphEdge(id);
        }

        public final int addFlowWeightedEdge(int from, int to, long weight, long capacity) {
            if (capacity == 0) {
                return addEdge(from, to, weight, 0, -1);
            } else {
                int lastEdgeCount = edgeCount;
                addEdge(to, from, -weight, 0, lastEdgeCount + entriesPerEdge());
                return addEdge(from, to, weight, capacity, lastEdgeCount);
            }
        }

        protected int entriesPerEdge() {
            return 1;
        }

        public final int addWeightedEdge(int from, int to, long weight) {
            return addFlowWeightedEdge(from, to, weight, 0);
        }

        public final int addSimpleEdge(int from, int to) {
            return addWeightedEdge(from, to, 0);
        }

        public final Edge edge(int id) {
            initEdges();
            return edges[id];
        }

        public final int firstOutbound(int vertex) {
            int id = firstOutbound[vertex];
            while (id != -1 && isRemoved(id)) {
                id = nextOutbound[id];
            }
            return id;
        }

        public final int nextOutbound(int id) {
            id = nextOutbound[id];
            while (id != -1 && isRemoved(id)) {
                id = nextOutbound[id];
            }
            return id;
        }

        public final int destination(int id) {
            return to[id];
        }

        protected final void initEdges() {
            if (edges == null) {
                edges = new Edge[from.length];
                for (int i = 0; i < edgeCount; i++) {
                    edges[i] = createEdge(i);
                }
            }
        }

        public final boolean flag(int id, int bit) {
            return (flags[id] >> bit & 1) != 0;
        }

        public final boolean isRemoved(int id) {
            return flag(id, REMOVED_BIT);
        }

        protected void ensureEdgeCapacity(int size) {
            if (from.length < size) {
                int newSize = Math.max(size, 2 * from.length);
                if (edges != null) {
                    edges = resize(edges, newSize);
                }
                from = resize(from, newSize);
                to = resize(to, newSize);
                nextOutbound = resize(nextOutbound, newSize);
                if (nextInbound != null) {
                    nextInbound = resize(nextInbound, newSize);
                }
                if (weight != null) {
                    weight = resize(weight, newSize);
                }
                if (capacity != null) {
                    capacity = resize(capacity, newSize);
                }
                if (reverseEdge != null) {
                    reverseEdge = resize(reverseEdge, newSize);
                }
                flags = resize(flags, newSize);
            }
        }

        protected final int[] resize(int[] array, int size) {
            int[] newArray = new int[size];
            System.arraycopy(array, 0, newArray, 0, array.length);
            return newArray;
        }

        private long[] resize(long[] array, int size) {
            long[] newArray = new long[size];
            System.arraycopy(array, 0, newArray, 0, array.length);
            return newArray;
        }

        private Edge[] resize(Edge[] array, int size) {
            Edge[] newArray = new Edge[size];
            System.arraycopy(array, 0, newArray, 0, array.length);
            return newArray;
        }

        protected class GraphEdge implements Edge {
            protected int id;

            protected GraphEdge(int id) {
                this.id = id;
            }

            public int getDestination() {
                return destination(id);
            }

        }

    }
}


import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.io.BufferedWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Osmanys Alonso (osmanys@gmail.com)
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        TaskE solver = new TaskE();
        int testCount = Integer.parseInt(in.next());
        for (int i = 1; i <= testCount; i++)
            solver.solve(i, in, out);
        out.close();
    }

    static class TaskE {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
            int n = in.readInt();
            int u, v, m = in.readInt();
            Graph g = new Graph(n);
            for (int i = 0; i < m; i++) {
                u = in.readInt() - 1;
                v = in.readInt() - 1;
                g.addSimpleEdge(u, v);
                g.addSimpleEdge(v, u);
            }
            boolean selected[] = new boolean[n];
            boolean visited[] = new boolean[n];
            int r = go(g, 0, visited, selected);
            out.printLine(r);
            for (int i = 0; i < n; i++) {
                if (selected[i])
                    out.print((i + 1) + " ");
            }
            out.printLine();
        }

        private int go(Graph g, int v, boolean visited[], boolean selected[]) {
            visited[v] = true;
            int next;
            Edge edge;
            boolean found = false;
            for (int e = g.firstOutbound(v); e != -1; e = g.nextOutbound(e)) {
                edge = g.edge(e);
                next = edge.getDestination();
                if (selected[next]) {
                    found = true;
                    break;
                }
            }
            int r = 0;
            if (!found) {
                selected[v] = true;
                r++;
            }
            for (int e = g.firstOutbound(v); e != -1; e = g.nextOutbound(e)) {
                edge = g.edge(e);
                next = edge.getDestination();
                if (!visited[next])
                    r += go(g, next, visited, selected);
            }
            return r;
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public int readInt() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public String readString() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                if (Character.isValidCodePoint(c)) {
                    res.appendCodePoint(c);
                }
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public String next() {
            return readString();
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void print(Object... objects) {
            for (int i = 0; i < objects.length; i++) {
                if (i != 0) {
                    writer.print(' ');
                }
                writer.print(objects[i]);
            }
        }

        public void printLine() {
            writer.println();
        }

        public void close() {
            writer.close();
        }

        public void printLine(int i) {
            writer.println(i);
        }

    }

    static interface Edge {
        public int getDestination();

    }

    static class Graph {
        public static final int REMOVED_BIT = 0;
        protected int vertexCount;
        protected int edgeCount;
        private int[] firstOutbound;
        private int[] firstInbound;
        private Edge[] edges;
        private int[] nextInbound;
        private int[] nextOutbound;
        private int[] from;
        private int[] to;
        private long[] weight;
        public long[] capacity;
        private int[] reverseEdge;
        private int[] flags;

        public Graph(int vertexCount) {
            this(vertexCount, vertexCount);
        }

        public Graph(int vertexCount, int edgeCapacity) {
            this.vertexCount = vertexCount;
            firstOutbound = new int[vertexCount];
            Arrays.fill(firstOutbound, -1);

            from = new int[edgeCapacity];
            to = new int[edgeCapacity];
            nextOutbound = new int[edgeCapacity];
            flags = new int[edgeCapacity];
        }

        public int addEdge(int fromID, int toID, long weight, long capacity, int reverseEdge) {
            ensureEdgeCapacity(edgeCount + 1);
            if (firstOutbound[fromID] != -1) {
                nextOutbound[edgeCount] = firstOutbound[fromID];
            } else {
                nextOutbound[edgeCount] = -1;
            }
            firstOutbound[fromID] = edgeCount;
            if (firstInbound != null) {
                if (firstInbound[toID] != -1) {
                    nextInbound[edgeCount] = firstInbound[toID];
                } else {
                    nextInbound[edgeCount] = -1;
                }
                firstInbound[toID] = edgeCount;
            }
            this.from[edgeCount] = fromID;
            this.to[edgeCount] = toID;
            if (capacity != 0) {
                if (this.capacity == null) {
                    this.capacity = new long[from.length];
                }
                this.capacity[edgeCount] = capacity;
            }
            if (weight != 0) {
                if (this.weight == null) {
                    this.weight = new long[from.length];
                }
                this.weight[edgeCount] = weight;
            }
            if (reverseEdge != -1) {
                if (this.reverseEdge == null) {
                    this.reverseEdge = new int[from.length];
                    Arrays.fill(this.reverseEdge, 0, edgeCount, -1);
                }
                this.reverseEdge[edgeCount] = reverseEdge;
            }
            if (edges != null) {
                edges[edgeCount] = createEdge(edgeCount);
            }
            return edgeCount++;
        }

        protected final GraphEdge createEdge(int id) {
            return new GraphEdge(id);
        }

        public final int addFlowWeightedEdge(int from, int to, long weight, long capacity) {
            if (capacity == 0) {
                return addEdge(from, to, weight, 0, -1);
            } else {
                int lastEdgeCount = edgeCount;
                addEdge(to, from, -weight, 0, lastEdgeCount + entriesPerEdge());
                return addEdge(from, to, weight, capacity, lastEdgeCount);
            }
        }

        protected int entriesPerEdge() {
            return 1;
        }

        public final int addWeightedEdge(int from, int to, long weight) {
            return addFlowWeightedEdge(from, to, weight, 0);
        }

        public final int addSimpleEdge(int from, int to) {
            return addWeightedEdge(from, to, 0);
        }

        public final Edge edge(int id) {
            initEdges();
            return edges[id];
        }

        public final int firstOutbound(int vertex) {
            int id = firstOutbound[vertex];
            while (id != -1 && isRemoved(id)) {
                id = nextOutbound[id];
            }
            return id;
        }

        public final int nextOutbound(int id) {
            id = nextOutbound[id];
            while (id != -1 && isRemoved(id)) {
                id = nextOutbound[id];
            }
            return id;
        }

        public final int destination(int id) {
            return to[id];
        }

        protected final void initEdges() {
            if (edges == null) {
                edges = new Edge[from.length];
                for (int i = 0; i < edgeCount; i++) {
                    edges[i] = createEdge(i);
                }
            }
        }

        public final boolean flag(int id, int bit) {
            return (flags[id] >> bit & 1) != 0;
        }

        public final boolean isRemoved(int id) {
            return flag(id, REMOVED_BIT);
        }

        protected void ensureEdgeCapacity(int size) {
            if (from.length < size) {
                int newSize = Math.max(size, 2 * from.length);
                if (edges != null) {
                    edges = resize(edges, newSize);
                }
                from = resize(from, newSize);
                to = resize(to, newSize);
                nextOutbound = resize(nextOutbound, newSize);
                if (nextInbound != null) {
                    nextInbound = resize(nextInbound, newSize);
                }
                if (weight != null) {
                    weight = resize(weight, newSize);
                }
                if (capacity != null) {
                    capacity = resize(capacity, newSize);
                }
                if (reverseEdge != null) {
                    reverseEdge = resize(reverseEdge, newSize);
                }
                flags = resize(flags, newSize);
            }
        }

        protected final int[] resize(int[] array, int size) {
            int[] newArray = new int[size];
            System.arraycopy(array, 0, newArray, 0, array.length);
            return newArray;
        }

        private long[] resize(long[] array, int size) {
            long[] newArray = new long[size];
            System.arraycopy(array, 0, newArray, 0, array.length);
            return newArray;
        }

        private Edge[] resize(Edge[] array, int size) {
            Edge[] newArray = new Edge[size];
            System.arraycopy(array, 0, newArray, 0, array.length);
            return newArray;
        }

        protected class GraphEdge implements Edge {
            protected int id;

            protected GraphEdge(int id) {
                this.id = id;
            }

            public int getDestination() {
                return destination(id);
            }

        }

    }
}


import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.io.BufferedWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Osmanys Alonso (osmanys@gmail.com)
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        TaskE solver = new TaskE();
        int testCount = Integer.parseInt(in.next());
        for (int i = 1; i <= testCount; i++)
            solver.solve(i, in, out);
        out.close();
    }

    static class TaskE {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
            int n = in.readInt();
            int u, v, m = in.readInt();
            Graph g = new Graph(n);
            for (int i = 0; i < m; i++) {
                u = in.readInt() - 1;
                v = in.readInt() - 1;
                g.addSimpleEdge(u, v);
                g.addSimpleEdge(v, u);
            }
            boolean selected[] = new boolean[n];
            boolean visited[] = new boolean[n];
            int r = go(g, 0, visited, selected);
            if (r <= n / 2) {
                out.printLine(r);
                for (int i = 0; i < n; i++) {
                    if (selected[i])
                        out.print((i + 1) + " ");
                }
            } else {
                out.printLine(n - r);
                for (int i = 0; i < n; i++) {
                    if (!selected[i])
                        out.print((i + 1) + " ");
                }
            }
            out.printLine();
        }

        private int go(Graph g, int v, boolean visited[], boolean selected[]) {
            visited[v] = true;
            int next;
            Edge edge;
            boolean found = false;
            for (int e = g.firstOutbound(v); e != -1; e = g.nextOutbound(e)) {
                edge = g.edge(e);
                next = edge.getDestination();
                if (selected[next]) {
                    found = true;
                    break;
                }
            }
            int r = 0;
            if (!found) {
                selected[v] = true;
                r++;
            }
            for (int e = g.firstOutbound(v); e != -1; e = g.nextOutbound(e)) {
                edge = g.edge(e);
                next = edge.getDestination();
                if (!visited[next])
                    r += go(g, next, visited, selected);
            }
            return r;
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public int readInt() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public String readString() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                if (Character.isValidCodePoint(c)) {
                    res.appendCodePoint(c);
                }
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public String next() {
            return readString();
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void print(Object... objects) {
            for (int i = 0; i < objects.length; i++) {
                if (i != 0) {
                    writer.print(' ');
                }
                writer.print(objects[i]);
            }
        }

        public void printLine() {
            writer.println();
        }

        public void close() {
            writer.close();
        }

        public void printLine(int i) {
            writer.println(i);
        }

    }

    static interface Edge {
        public int getDestination();

    }

    static class Graph {
        public static final int REMOVED_BIT = 0;
        protected int vertexCount;
        protected int edgeCount;
        private int[] firstOutbound;
        private int[] firstInbound;
        private Edge[] edges;
        private int[] nextInbound;
        private int[] nextOutbound;
        private int[] from;
        private int[] to;
        private long[] weight;
        public long[] capacity;
        private int[] reverseEdge;
        private int[] flags;

        public Graph(int vertexCount) {
            this(vertexCount, vertexCount);
        }

        public Graph(int vertexCount, int edgeCapacity) {
            this.vertexCount = vertexCount;
            firstOutbound = new int[vertexCount];
            Arrays.fill(firstOutbound, -1);

            from = new int[edgeCapacity];
            to = new int[edgeCapacity];
            nextOutbound = new int[edgeCapacity];
            flags = new int[edgeCapacity];
        }

        public int addEdge(int fromID, int toID, long weight, long capacity, int reverseEdge) {
            ensureEdgeCapacity(edgeCount + 1);
            if (firstOutbound[fromID] != -1) {
                nextOutbound[edgeCount] = firstOutbound[fromID];
            } else {
                nextOutbound[edgeCount] = -1;
            }
            firstOutbound[fromID] = edgeCount;
            if (firstInbound != null) {
                if (firstInbound[toID] != -1) {
                    nextInbound[edgeCount] = firstInbound[toID];
                } else {
                    nextInbound[edgeCount] = -1;
                }
                firstInbound[toID] = edgeCount;
            }
            this.from[edgeCount] = fromID;
            this.to[edgeCount] = toID;
            if (capacity != 0) {
                if (this.capacity == null) {
                    this.capacity = new long[from.length];
                }
                this.capacity[edgeCount] = capacity;
            }
            if (weight != 0) {
                if (this.weight == null) {
                    this.weight = new long[from.length];
                }
                this.weight[edgeCount] = weight;
            }
            if (reverseEdge != -1) {
                if (this.reverseEdge == null) {
                    this.reverseEdge = new int[from.length];
                    Arrays.fill(this.reverseEdge, 0, edgeCount, -1);
                }
                this.reverseEdge[edgeCount] = reverseEdge;
            }
            if (edges != null) {
                edges[edgeCount] = createEdge(edgeCount);
            }
            return edgeCount++;
        }

        protected final GraphEdge createEdge(int id) {
            return new GraphEdge(id);
        }

        public final int addFlowWeightedEdge(int from, int to, long weight, long capacity) {
            if (capacity == 0) {
                return addEdge(from, to, weight, 0, -1);
            } else {
                int lastEdgeCount = edgeCount;
                addEdge(to, from, -weight, 0, lastEdgeCount + entriesPerEdge());
                return addEdge(from, to, weight, capacity, lastEdgeCount);
            }
        }

        protected int entriesPerEdge() {
            return 1;
        }

        public final int addWeightedEdge(int from, int to, long weight) {
            return addFlowWeightedEdge(from, to, weight, 0);
        }

        public final int addSimpleEdge(int from, int to) {
            return addWeightedEdge(from, to, 0);
        }

        public final Edge edge(int id) {
            initEdges();
            return edges[id];
        }

        public final int firstOutbound(int vertex) {
            int id = firstOutbound[vertex];
            while (id != -1 && isRemoved(id)) {
                id = nextOutbound[id];
            }
            return id;
        }

        public final int nextOutbound(int id) {
            id = nextOutbound[id];
            while (id != -1 && isRemoved(id)) {
                id = nextOutbound[id];
            }
            return id;
        }

        public final int destination(int id) {
            return to[id];
        }

        protected final void initEdges() {
            if (edges == null) {
                edges = new Edge[from.length];
                for (int i = 0; i < edgeCount; i++) {
                    edges[i] = createEdge(i);
                }
            }
        }

        public final boolean flag(int id, int bit) {
            return (flags[id] >> bit & 1) != 0;
        }

        public final boolean isRemoved(int id) {
            return flag(id, REMOVED_BIT);
        }

        protected void ensureEdgeCapacity(int size) {
            if (from.length < size) {
                int newSize = Math.max(size, 2 * from.length);
                if (edges != null) {
                    edges = resize(edges, newSize);
                }
                from = resize(from, newSize);
                to = resize(to, newSize);
                nextOutbound = resize(nextOutbound, newSize);
                if (nextInbound != null) {
                    nextInbound = resize(nextInbound, newSize);
                }
                if (weight != null) {
                    weight = resize(weight, newSize);
                }
                if (capacity != null) {
                    capacity = resize(capacity, newSize);
                }
                if (reverseEdge != null) {
                    reverseEdge = resize(reverseEdge, newSize);
                }
                flags = resize(flags, newSize);
            }
        }

        protected final int[] resize(int[] array, int size) {
            int[] newArray = new int[size];
            System.arraycopy(array, 0, newArray, 0, array.length);
            return newArray;
        }

        private long[] resize(long[] array, int size) {
            long[] newArray = new long[size];
            System.arraycopy(array, 0, newArray, 0, array.length);
            return newArray;
        }

        private Edge[] resize(Edge[] array, int size) {
            Edge[] newArray = new Edge[size];
            System.arraycopy(array, 0, newArray, 0, array.length);
            return newArray;
        }

        protected class GraphEdge implements Edge {
            protected int id;

            protected GraphEdge(int id) {
                this.id = id;
            }

            public int getDestination() {
                return destination(id);
            }

        }

    }
}