求图的割点

#include <bits/stdc++.h>using namespace std;int n, m, root, sum;int first[9], next[25], u[25], v[25];int num[9], low[9], flag[9], indexs;void add(int x, int y){    u[sum] = x, v[sum] = y;    next[sum] = first[x];    first[x] = sum;    sum++;}void dfs(int cur, int father){    int child = 0, k;    indexs++;    num[cur] = indexs;    low[cur] = indexs;    k = first[cur];    while(k != -1)    {        if(num[v[k]] == 0)        {            child++;            dfs(v[k], cur);            low[cur] = min(low[cur], low[v[k]]);            if(cur != root && low[v[k]] >= num[cur])                flag[cur] = 1;            if(cur == root && child == 2)                flag[cur] = 1;        }        else if(v[k] != father)        {            low[cur] = min(low[cur], num[v[k]]);        }        k = next[k];    }    return ;}int main(){    int i, x, y;    scanf("%d %d", &n, &m);    for(i = 1; i <= n; i++)        first[i] = -1;    for(i = 1; i <= m; i++)    {        scanf("%d %d", &x, &y);        add(x, y);        add(y, x);    }    root = 1;    dfs(1, root);    for(i = 1; i <= n; i++)        if(flag[i])            cout << i << endl;    return 0;}