模板——Tarjan

#include <cstdio>
#include <cstring>
#include <iostream>
#include <vector>
using namespace std;
const int maxn=;
vector<int>tu[maxn];
vector<int>lt[maxn];
int n,m,lts=;
int js=;
int dfn[maxn],low[maxn];
int zhan[maxn],top=;
bool isins[maxn];
void tarjan(int i)
{
    int j;
    dfn[i]=low[i]=++js;
    isins[i]=;
    zhan[top++]=i;
    for(int j=;j<tu[i].size();j++)
    {
        int tp=tu[i][j];
        if(dfn[tp]==-)
            tarjan(tp),
            low[i]=min(low[i],low[tp]);
        else if(isins[tp])
            low[i]=min(low[i],dfn[tp]);
    }
    if(dfn[i]==low[i])
    {
        lts++;
        do{
            j=zhan[--top];
            isins[j]=;
            lt[lts].push_back(j);
        }while(i!=j);
    }
}
void solve(int n)
{
    memset(dfn,-,sizeof dfn);
    memset(low,-,sizeof low);
    memset(zhan,-,sizeof zhan);
    memset(isins,,sizeof isins);
    for(int i=;i<n;i++)
        if(dfn[i]==-)
            tarjan(i);
}
int main()
{
    scanf("%d%d",&n,&m);
    for(int i=;i<=m;i++)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        tu[x].push_back(y);
    }
    solve(n);
    for(int i=;i<=lts;i++)
    {
        cout<<i<<":";
        for(int j=;j<lt[i].size();j++)
            cout<<lt[i][j]<<" ";
        cout<<endl;
    }
    return ;
}