Reachable Nodes With Restrictions
<p>There is an undirected tree with <code>n</code> nodes labeled from <code>0</code> to <code>n - 1</code> and <code>n - 1</code> edges.</p>

<p>You are given a 2D integer array <code>edges</code> of length <code>n - 1</code> where <code>edges[i] = [a<sub>i</sub>, b<sub>i</sub>]</code> indicates that there is an edge between nodes <code>a<sub>i</sub></code> and <code>b<sub>i</sub></code> in the tree. You are also given an integer array <code>restricted</code> which represents <strong>restricted</strong> nodes.</p>

<p>Return <em>the <strong>maximum</strong> number of nodes you can reach from node </em><code>0</code><em> without visiting a restricted node.</em></p>

<p>Note that node <code>0</code> will <strong>not</strong> be a restricted node.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/2300-2399/2368.Reachable%20Nodes%20With%20Restrictions/images/ex1drawio.png" style="width: 402px; height: 322px;" />
<pre>
<strong>Input:</strong> n = 7, edges = [[0,1],[1,2],[3,1],[4,0],[0,5],[5,6]], restricted = [4,5]
<strong>Output:</strong> 4
<strong>Explanation:</strong> The diagram above shows the tree.
We have that [0,1,2,3] are the only nodes that can be reached from node 0 without visiting a restricted node.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/2300-2399/2368.Reachable%20Nodes%20With%20Restrictions/images/ex2drawio.png" style="width: 412px; height: 312px;" />
<pre>
<strong>Input:</strong> n = 7, edges = [[0,1],[0,2],[0,5],[0,4],[3,2],[6,5]], restricted = [4,2,1]
<strong>Output:</strong> 3
<strong>Explanation:</strong> The diagram above shows the tree.
We have that [0,5,6] are the only nodes that can be reached from node 0 without visiting a restricted node.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>2 &lt;= n &lt;= 10<sup>5</sup></code></li>
	<li><code>edges.length == n - 1</code></li>
	<li><code>edges[i].length == 2</code></li>
	<li><code>0 &lt;= a<sub>i</sub>, b<sub>i</sub> &lt; n</code></li>
	<li><code>a<sub>i</sub> != b<sub>i</sub></code></li>
	<li><code>edges</code> represents a valid tree.</li>
	<li><code>1 &lt;= restricted.length &lt; n</code></li>
	<li><code>1 &lt;= restricted[i] &lt; n</code></li>
	<li>All the values of <code>restricted</code> are <strong>unique</strong>.</li>
</ul>
Tree; Depth-First Search; Breadth-First Search; Union Find; Graph; Array; Hash Table
class Solution {
    private List<Integer>[] g;
    private boolean[] vis;

    public int reachableNodes(int n, int[][] edges, int[] restricted) {
        g = new List[n];
        vis = new boolean[n];
        Arrays.setAll(g, k -> new ArrayList<>());
        for (var e : edges) {
            int a = e[0], b = e[1];
            g[a].add(b);
            g[b].add(a);
        }
        for (int i : restricted) {
            vis[i] = true;
        }
        return dfs(0);
    }

    private int dfs(int i) {
        vis[i] = true;
        int ans = 1;
        for (int j : g[i]) {
            if (!vis[j]) {
                ans += dfs(j);
            }
        }
        return ans;
    }
}