关节点算法

#include <iostream>
#include <cstdio>
#include <cstring>
#include <vector>

using namespace std;
#define MAXN 1000
int low[MAXN],visit[MAXN]; // low[i] = min(visit[i],visist[j],low[w]); j 是 回路的父值，w是儿子值
int pointNum,edgeNum;
int count; // 统计遍历的顺序

int dfsArticul(vector<vector<int> > G,int v0) { // 最小的low[]值
    int min = visit[v0] = ++count;
    for (int i = 0;i < G[v0].size();i++) {
        int w = G[v0][i];
        if (visit[w] == 0) {
            low[w] = dfsArticul(G,w);
            if (low[w] < min) min = low[w];
            if (low[w] >= visit[v0]) cout << v0 << endl;
        }
        else if (visit[w] < min) {
            min = visit[w];
        }
    }
    return low[v0] = min;
}

void findArticul(vector <vector<int> > G) { 
    visit[0] = 1;
    count = 1;
    for (int i = 1;i < pointNum;i++) {
        visit[i] = 0;
    }
    int p = G[0][0];
    dfsArticul(G,p);
    if (count < pointNum) { // 父节点是否有两个子树
        cout << 0 << endl;
        for (int i = 1;i < G[0].size();i++) {
            int w = G[0][i];
            if (visit[w] == 0)
                dfsArticul(G,w);
        }
    }
}

int main () {
    // freopen("1.in","r",stdin);
    vector <vector<int> > G; // 邻接表
    cin >> pointNum >> edgeNum; // 点的个数，边的个数
    G.resize(pointNum + 1);
    for (int i = 0;i < pointNum;i++) G[i].clear();
    for (int i = 0;i < edgeNum;i++) {
        int x,y;
        cin >> x >> y; // 边的起点，和终点
        G[x].push_back(y);
        G[y].push_back(x);
    }
    findArticul(G);
}