tarjan算法

这个算法网上很容易找到详解，其实认真看一遍百度百科也就懂得七七八八了

再附详解地址，这位博主也是转别人的，但是那个别人的博客打不开了

https://blog.youkuaiyun.com/qq_34374664/article/details/77488976

这个算法的核心思想：将连通分量的各个点用一个点表示。

#include <iostream>
#include <cstring>
#include <cmath>
#include <cstdio>
#include <stack>
#include <algorithm>

using namespace std;

#define INF 0x3f3f3f3f
#define MAXN 551

int DFN[MAXN], Low[MAXN];
int vis[MAXN], sta_ck[MAXN];
int Index, cnt, tot;
int n;

struct Node
{
    int to;
    int next;
}node[MAXN];
int head[MAXN];

//用head作为头指针指向下一个结点下标，让next指向head指向的下标后，head指向该结点
void add(int x, int y)
{
    node[++cnt].next = head[x];
    node[cnt].to = y;
    head[x] = cnt;
}

void tarjan(int x)
{
    DFN[x] = Low[x] = ++tot;
    sta_ck[++Index] = x;
    vis[x] = 1;
    for(int i = head[x]; i != -1; i = node[i].next)
    {
        if(!DFN[node[i].to])
        {
            tarjan(node[i].to);
            Low[x] = min(Low[x], Low[node[i].to]);
        }
        else if(vis[node[i].to])
            Low[x] = min(Low[x], DFN[node[i].to]);
    }
    if(Low[x] == DFN[x])
    {
        do
        {
            cout << sta_ck[Index] <<" ";
            vis[sta_ck[Index]]=0;
            Index--;
        }while(x != sta_ck[Index + 1]);
        cout << endl;
    }

}

int main()
{
    memset(head, -1, sizeof(head));
    memset(DFN, 0, sizeof(DFN));
    memset(Low, 0, sizeof(Low));
    int n, m;
    cin >>n >>m;
    int x, y;
    for(int i = 1; i <= m; ++i)
    {
        cin >>x >>y;
        add(x, y);
    }
    for(int i = 1; i <= n; ++i)
        if(!DFN[i])
        tarjan(i);
    return 0;
}