Is Graph Bipartite
<p>There is an <strong>undirected</strong> graph with <code>n</code> nodes, where each node is numbered between <code>0</code> and <code>n - 1</code>. You are given a 2D array <code>graph</code>, where <code>graph[u]</code> is an array of nodes that node <code>u</code> is adjacent to. More formally, for each <code>v</code> in <code>graph[u]</code>, there is an undirected edge between node <code>u</code> and node <code>v</code>. The graph has the following properties:</p>

<ul>
	<li>There are no self-edges (<code>graph[u]</code> does not contain <code>u</code>).</li>
	<li>There are no parallel edges (<code>graph[u]</code> does not contain duplicate values).</li>
	<li>If <code>v</code> is in <code>graph[u]</code>, then <code>u</code> is in <code>graph[v]</code> (the graph is undirected).</li>
	<li>The graph may not be connected, meaning there may be two nodes <code>u</code> and <code>v</code> such that there is no path between them.</li>
</ul>

<p>A graph is <strong>bipartite</strong> if the nodes can be partitioned into two independent sets <code>A</code> and <code>B</code> such that <strong>every</strong> edge in the graph connects a node in set <code>A</code> and a node in set <code>B</code>.</p>

<p>Return <code>true</code><em> if and only if it is <strong>bipartite</strong></em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0700-0799/0785.Is%20Graph%20Bipartite/images/bi2.jpg" style="width: 222px; height: 222px;" />
<pre>
<strong>Input:</strong> graph = [[1,2,3],[0,2],[0,1,3],[0,2]]
<strong>Output:</strong> false
<strong>Explanation:</strong> There is no way to partition the nodes into two independent sets such that every edge connects a node in one and a node in the other.</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0700-0799/0785.Is%20Graph%20Bipartite/images/bi1.jpg" style="width: 222px; height: 222px;" />
<pre>
<strong>Input:</strong> graph = [[1,3],[0,2],[1,3],[0,2]]
<strong>Output:</strong> true
<strong>Explanation:</strong> We can partition the nodes into two sets: {0, 2} and {1, 3}.</pre>

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

<ul>
	<li><code>graph.length == n</code></li>
	<li><code>1 &lt;= n &lt;= 100</code></li>
	<li><code>0 &lt;= graph[u].length &lt; n</code></li>
	<li><code>0 &lt;= graph[u][i] &lt;= n - 1</code></li>
	<li><code>graph[u]</code>&nbsp;does not contain&nbsp;<code>u</code>.</li>
	<li>All the values of <code>graph[u]</code> are <strong>unique</strong>.</li>
	<li>If <code>graph[u]</code> contains <code>v</code>, then <code>graph[v]</code> contains <code>u</code>.</li>
</ul>
Depth-First Search; Breadth-First Search; Union Find; Graph
class Solution {
    private int[] color;
    private int[][] g;

    public boolean isBipartite(int[][] graph) {
        int n = graph.length;
        color = new int[n];
        g = graph;
        for (int i = 0; i < n; ++i) {
            if (color[i] == 0 && !dfs(i, 1)) {
                return false;
            }
        }
        return true;
    }

    private boolean dfs(int a, int c) {
        color[a] = c;
        for (int b : g[a]) {
            if (color[b] == c || (color[b] == 0 && !dfs(b, -c))) {
                return false;
            }
        }
        return true;
    }
}
