图论：割点和桥

#include<iostream>
#include<cstdio>
#include<cstring>
#include<vector>
using namespace std;
const int maxn = 1200;
const int INF = 0x3ffffff;
int num[maxn],parent[maxn],low[maxn],vis[maxn],cnt;
vector <int> vc[maxn];
int MIN(int x,int y)
{
    return x<y?x:y;
}
void AssignNum(int v) //建立dfs深搜树 
{
    int i,w;
    num[v]=cnt++;
    vis[v]=1;
    for(i=0;i<vc[v].size();i++){
        w=vc[v][i];
        if(vis[w]==0){
            parent[w]=v;
            AssignNum(w);
        }
    }
}
void AssignLow(int v) //建立low数组，打印割点 
{
    int i,w;
    low[v]=num[v];
    for(i=0;i<vc[v].size();i++){
        w=vc[v][i];
        if(num[w]>num[v]){
            AssignLow(w);
            if(low[w]>=num[v]){
                printf("The gedian is %d\n",v);
            }
            low[v]=MIN(low[v],low[w]);
        }
        else if(parent[v]!=w){
            low[v]=MIN(low[v],num[w]);
        }
    }
}
void FindArt(int v) //打印割点 = AssignNum+AssignLow; 
{
    int i,w;
    low[v]=num[v]=cnt++;
    vis[v]=1;
    for(i=0;i<vc[v].size();i++){
        w=vc[v][i];
        if(!vis[w]){
            parent[w]=v;
            FindArt(w);
            if(low[w]>=num[v]) printf("The articulation point is %d\n",v);
            low[v]=MIN(low[v],low[w]);
        }
        else if(parent[v]!=w) low[v]=MIN(low[v],num[w]);
    }
}
int main(void)
{
    int n,m,i,j,x,y;
    cin>>n>>m;
    cnt=1;
    memset(vis,0,sizeof(vis));
    for(i=0;i<m;i++){
        scanf("%d%d",&x,&y);
        vc[x].push_back(y);
        vc[y].push_back(x);
    }
    //AssignNum(3);
    //AssignLow(3);
    FindArt(4); //根节点是割点 
    return 0;
}

/*
7 8
1 2
2 3
3 4
4 1
4 7
4 5
7 5
3 6
*/