poj1144（求割顶模板题）

#include<iostream>
#include<algorithm>
#include<stdio.h>
#include<math.h>
#include<cstring>
#include<string>
#include<vector>
#define inf 0x3f3f3f3f
#define pi acos(-1.0)
#define eps 10e-6
#define N 105
using namespace std;
char s[10000];
vector<int> G
;
int pre
,iscut
,low
;
int dfs_clock;
int dfs(int u,int fa)
{
    int lowu = pre[u] = ++dfs_clock;
    int child = 0,len = G[u].size();
    for(int i = 0; i < len; i++)
    {
        int v = G[u][i];
        if(!pre[v])
        {
            child++;
            int lowv = dfs(v,u);
            lowu = min(lowu,lowv);
            if(lowv >= pre[u])
                iscut[u] = 1;//如果是u是割点则标记为1
        }
        else if(pre[v] < pre[u] && v != fa)
            lowu = min(lowu,pre[v]);
    }
    if(fa < 0 && child == 1) iscut[u] = 0;
    low[u] = lowu;//可以不用low数组
    return lowu;
}
int main()
{
     int n;
     while(scanf("%d",&n) && n)
     {
         getchar();
         int i;
         for(i = 0; i <= n; i++)
            G[i].clear();
         int u,v;
         while(scanf("%d",&u),u)//注意输入问题
         {
            while (getchar()!='\n')
            {
                scanf("%d",&v);
                G[u].push_back(v);
                G[v].push_back(u);
            }
         }
         dfs_clock = 0;
         memset(iscut,0,sizeof(iscut));
         memset(pre,0,sizeof(pre));
         dfs(1,-1);
         int cnt = 0;
         for(i = 1; i <= n; i++)
            if(iscut[i] == 1)
                cnt++;
        printf("%d\n",cnt);
     }
    return 0;
}