POJ 1144 Network （求割点）

题意：

给定一幅无向图， 求出图的割点。

割点模板：http://www.cnblogs.com/Jadon97/p/8328750.html

分析：

输入有点麻烦， 用stringsteam 会比较简单

#include<cstdio>
#include<iostream>
#include<queue>
#include<cstring>
#include<string>
#include<sstream>
#include<map>
#include<stack>
#include<vector>
#include<algorithm>
#include<cmath>
#define rep(i,a,b) for(int i = a; i < b; i++)
#define _rep(i,a,b) for(int i = a; i <= b; i++)
using namespace std;
const int maxn = 107;
vector<int> G[maxn];
int n, Index, root, ans;
int dfn[maxn], low[maxn], cut[maxn];
void tarjan(int u, int father){
    dfn[u] = Index;
    low[u] = dfn[u];
    Index++;
    int child = 0;
    for(int i = 0; i < G[u].size(); i++){
        int v = G[u][i];
        if(!dfn[v]){
            child++;
            tarjan(v, u);
            low[u] = min(low[v], low[u]);
            if(low[v] >= dfn[u] && u != root) cut[u] = 1;
            if(u == root && child == 2) cut[u] = 1;
        }else if(v != father){
            low[u] = min(low[u], dfn[v]);
        }
    }
}
int main(){
    ios::sync_with_stdio(false);
    while(cin >> n && n){
        Index = 1;
        memset(dfn, 0, sizeof(dfn));
        memset(low, 0, sizeof(low));
        memset(cut, 0, sizeof(cut));
        _rep(i,1,n) G[i].clear();
        root = 1, ans = 0;
        string input;
        while(getline(cin, input)){
            if(input[0] == '0') break;
            stringstream ss(input);
            int u, v;
            ss >> u;
            while(ss >> v){
                G[u].push_back(v);
                G[v].push_back(u);
            }
        }
        tarjan(1,1);
        _rep(i,1,n) if(cut[i]) ans++;
        cout << ans << "
";
    }
    return 0;
}