poj 1144 Network(割点入门）

http://poj.org/problem?id=1144

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<vector>
using namespace std;

const int mx=105;
vector<int>map[mx];
int dfn[mx],low[mx],vs[mx],flag[mx];
int dfn_cut;

void dfs(int v,int u)
{
    int child=0;
    dfn[v]=low[v]=++dfn_cut;
    vs[v]=1;
    for (int i=0;i<map[v].size();i++)
    {
        int w=map[v][i];
        if (!vs[w])
        {
            child++;
            dfs(w,v);
            low[v]=min(low[v],low[w]);
            if (child>1&&v==1) flag[v]=1;
            if (v!=1&&low[w]>=dfn[v]) flag[v]=1;
        }
        else if (w!=u&&u!=-1) low[v]=min(low[v],dfn[w]);
    }
}

int main()
{
    int n,x,y;
    while (~scanf("%d",&n)&&n)
    {
        for (int i=1;i<=n;i++) map[i].clear();
        while (~scanf("%d",&x)&&x)
        {
            char c;
            while (c=getchar()!='
')
            {
                scanf("%d",&y);
                map[x].push_back(y);
                map[y].push_back(x);
            }
        }
        memset(low,0,sizeof(low));
        memset(dfn,0,sizeof(dfn));
        memset(vs,0,sizeof(vs));
        memset(flag,0,sizeof(flag));
        dfn_cut=0;
        dfs(1,-1);
        int ans=0;
        for (int i=1;i<=n;i++) ans+=flag[i];
        printf("%d
",ans);
    }
}

终于做了一道割点题，虽然还不太懂