/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package IO;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
    
/**
 * 
 * @author dannocz
 */
public class InputReader {
    
    public static Input readFile(String filename){
        try {
              
              /*  Sets up a file reader to read the file passed on the command
          77        line one character at a time */
              FileReader input = new FileReader(filename);
              
              /* Filter FileReader through a Buffered read to read a line at a
                 time */
              BufferedReader bufRead = new BufferedReader(input);
              
              String line;    // String that holds current file line
              int count = 0;  // Line number of count 
              ArrayList<String> cases= new ArrayList<String>();
              
              // Read first line
              line = bufRead.readLine();
              int noTestCases=Integer.parseInt(line);
              count++;
              
              // Read through file one line at time. Print line # and line
              while (count<=noTestCases){
                  //System.out.println("Reading. "+count+": "+line);
                  line = bufRead.readLine();
                  cases.add(line);
                  count++;
              }
              
              bufRead.close();
              
              return new Input(noTestCases,cases);
              
          }catch (ArrayIndexOutOfBoundsException e){
              /* If no file was passed on the command line, this expception is
              generated. A message indicating how to the class should be
              called is displayed */
              e.printStackTrace();        
  
          }catch (IOException e){
              // If another exception is generated, print a stack trace
              e.printStackTrace();
          }
        
        return null;
          
      }// end main
    }

package util;

import java.math.BigInteger;

public class CombinationGenerator {

  private int[] a;
  private int n;
  private int r;
  private BigInteger numLeft;
  private BigInteger total;

  //------------
  // Constructor
  //------------

  public CombinationGenerator (int n, int r) {
    if (r > n) {
      throw new IllegalArgumentException ();
    }
    if (n < 1) {
      throw new IllegalArgumentException ();
    }
    this.n = n;
    this.r = r;
    a = new int[r];
    BigInteger nFact = getFactorial (n);
    BigInteger rFact = getFactorial (r);
    BigInteger nminusrFact = getFactorial (n - r);
    total = nFact.divide (rFact.multiply (nminusrFact));
    reset ();
  }

  //------
  // Reset
  //------

  public void reset () {
    for (int i = 0; i < a.length; i++) {
      a[i] = i;
    }
    numLeft = new BigInteger (total.toString ());
  }

  //------------------------------------------------
  // Return number of combinations not yet generated
  //------------------------------------------------

  public BigInteger getNumLeft () {
    return numLeft;
  }

  //-----------------------------
  // Are there more combinations?
  //-----------------------------

  public boolean hasMore () {
    return numLeft.compareTo (BigInteger.ZERO) == 1;
  }

  //------------------------------------
  // Return total number of combinations
  //------------------------------------

  public BigInteger getTotal () {
    return total;
  }

  //------------------
  // Compute factorial
  //------------------

  private static BigInteger getFactorial (int n) {
    BigInteger fact = BigInteger.ONE;
    for (int i = n; i > 1; i--) {
      fact = fact.multiply (new BigInteger (Integer.toString (i)));
    }
    return fact;
  }

  //--------------------------------------------------------
  // Generate next combination (algorithm from Rosen p. 286)
  //--------------------------------------------------------

  public int[] getNext () {

    if (numLeft.equals (total)) {
      numLeft = numLeft.subtract (BigInteger.ONE);
      return a;
    }

    int i = r - 1;
    while (a[i] == n - r + i) {
      i--;
    }
    a[i] = a[i] + 1;
    for (int j = i + 1; j < r; j++) {
      a[j] = a[i] + j - i;
    }

    numLeft = numLeft.subtract (BigInteger.ONE);
    return a;

  }
}
