Tarjan 割点，桥

/*         ggg   ggg
        ggggggg ggggggg
      ggggggggggggggggggg
        ggggggggggggggg
          ggggggggggg
            ggggggg
              ggg
               g
*/
/*  gyt
       Live up to every day            */

#include<cstdio>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<cstring>
#include<queue>
#include<set>
#include<string>
#include<map>
#include <time.h>
#define PI acos(-1)
using namespace std;
typedef long long ll;
typedef double db;
const int maxn = 500+5;
const ll maxm = 1e7;
const int mod = 1e9 + 7;
const int INF = 0x3f3f3f;
const ll inf = 1e15 + 5;
const db eps = 1e-9;
#define N 201
vector<int>G[N];
int n,m,low[N],dfn[N];
bool is_cut[N];
int father[N];
int tim=0;

void init() {
    memset(dfn, -1, sizeof(dfn));
    memset(father, 0, sizeof(father));
    memset(low, -1, sizeof(low));
    memset(is_cut, 0, sizeof(is_cut));
}
void Tarjan(int i, int Father) {
    father[i] = Father;
    dfn[i] = low[i] = tim++;
    for (int j = 0; j < G[i].size(); j++) {
        int k = G[i][j];
        if (dfn[k]==-1) {
            Tarjan(k, i);
            low[i] = min(low[i], low[k]);
        }
        else if(Father != k) {
            low[i] = min(low[i], dfn[k]);
        }
    }
}
void cnt() {
    int rootson=0;
    Tarjan(1, 0);
    for(int i=2;i<=n;++i){
        int v=father[i];
        if(v==1)
        rootson++;/*统计根节点子树的个数，根节点的子树个数>=2,就是割点*/
        else{
            if(low[i]>=dfn[v])/*割点的条件*/
            is_cut[v]=true;
        }
    }
    if(rootson>1)
        is_cut[1]=true;
    for(int i=1;i<=n;++i)
        if(is_cut[i])
            printf("%d
",i);
    for(int i=1;i<=n;++i){
        int v=father[i];
        if(v>0&&low[i]>dfn[v])/*桥的条件*/
            printf("%d,%d
",v,i);
    }
}
void solve() {
    init();
  //  scanf("%d%d", &n, &m);
    cin >> n >> m;
    for (int i = 0; i < N; i++)  G[i].clear();
    for (int i = 0; i < m; i++) {
        int a, b;  scanf("%d%d", &a, &b);
        G[a].push_back(b);
        G[b].push_back(a);
    }
    int rootson=0;
    cnt();
}
int main() {
    int t = 1;
    //scanf("%d", &t);
    while(t--)
        solve();
    return 0;
}