二分图判定

1bool isBipartite(int V, vector<vector<int>>& adj) {
2    vector<int> color(V, -1);
3    for (int i = 0; i < V; i++) {
4        if (color[i] != -1) continue;
5        color[i] = 0;
6        queue<int> q;
7        q.push(i);
8        while (!q.empty()) {
9            int u = q.front(); q.pop();
10            for (int v : adj[u]) {
11                if (color[v] == -1) {
12                    color[v] = 1 - color[u];
13                    q.push(v);
14                } else if (color[v] == color[u])
15                    return false;
16            }
17        }
18    }
19    return true;
20}