有向图强连通分支的Tarjan算法讲解 + HDU 1269 连通图 Tarjan 结题报告

#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<vector>
#include<queue>
#define INF 0xfffffff
#define MAX 101000

using namespace std;

int n,m,k,Time,vis[MAX],low[MAX],dfn[MAX],black,e,Stack[MAX];

vector<vector<int> >G;

void Tarjan(int u)
{
    vis[u]=1;
    Stack[++k]=u;
    low[u]=dfn[u]=Time++;

    int v,len=G[u].size(),i;

    for(i=0;i<len;i++)
    {
        v=G[u][i];

        if(!dfn[v])
        {
            Tarjan(v);
            low[u]=min(low[u],low[v]);
        }

        else if(vis[v])
        {
            low[u]=min(low[u],dfn[v]);
        }
    }

    if(dfn[u]==low[u])
    {
        do
        {
            v=Stack[k--];
            e++;
            vis[v]=0;
        }while(u!=v);
        black++;
    }
}

int main()
{
    int i,j,a,b;

    while(scanf("%d%d",&n,&m),n+m)
    {
        Time=1;
        k=e=black=0;
        memset(vis,0,sizeof(vis));
        memset(low,0,sizeof(low));
        memset(dfn,0,sizeof(dfn));
        memset(Stack,0,sizeof(Stack));

        G.clear();
        G.resize(n+1);

        for(i=1;i<=m;i++)
        {
            scanf("%d%d",&a,&b);
            G[a].push_back(b);
        }

        Tarjan(1);

        if(e==n && black==1)
            printf("Yes\n");
        else
            printf("No\n");
    }
    return 0;
}