有向图----强连通分量问题（Kosaraju算法）

public class KosarajuSharirSCC {
    private boolean[] marked;     // 已访问过的顶点
    private int[] id;             // 强连通分量的标识符
    private int count;            //强连通分量的数量

    public KosarajuSharirSCC(Digraph G) {
        marked = new boolean[G.V()];
        id = new int[G.V()];
        DepthFirstOrder dfs = new DepthFirstOrder(G.reverse());//区别
        for (int v : dfs.reversePost()) {//区别
            if (!marked[v]) {
                dfs(G, v);
                count++;
            }
        }
    }
    private void dfs(Digraph G, int v) { 
        marked[v] = true;
        id[v] = count;
        for (int w : G.adj(v)) {
            if (!marked[w]) dfs(G, w);
        }
    }
    public int count() { return count; }
    public boolean stronglyConnected(int v, int w) { return id[v] == id[w]; }
}