比起双连通的Tarjan我倒是觉得反而简单多了。思想和双连通分量是同一个模式。

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <stack>
using namespace std;

const int N = 1e5;
int dfn[N], scc_id[N];
int deep, scc_cnt;
stack <int> s;

int dfs(int u)
{
    int lowu = dfn[u] = ++deep;
    s.push(u);
    for(int i = head[u]; ~i; i = e[i].next) {
        int v = e[i].v;
        if(!dfn[v]) {
            int lowv = dfs(v);
            lowu = min(lowu, lowv);
        }
        else if(!scc_id[v]) {//连到栈中的还未标号的祖先们
            lowu = min(lowu, dfn[v]);
        }//利用当前scc中的点来更新
    }
    if(lowu == dfn[u]) {//只有最先发现的点满足这个条件
        scc_cnt++;
        while(1) {
            int x = s.top(); s.pop();
            scc_id[x] = scc_cnt;
            if(x == u) break;
        }
    }
    return lowu;
}

void tarjan()
{
    for(int i = 0; i < n; i++) {
        dfn[i] = scc_id[i] = 0;
    }
    deep = scc_cnt = 0;
    for(int i = 0; i < n; i++) {
        if(!dfn[i]) dfs(i);
    }
}

int main()
{

    return 0;
}

【强连通】强连通模板 Tarjan