uva 315 (poj 1144 求割点)

题意：给你一张无向图，求割点的个数。

思路：输入稍微处理一下接着直接套模版。

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <queue>
#include <stack>
#include <vector>
#include <set>
#include <map>
#define MP(a, b) make_pair(a, b)
#define PB(a) push_back(a)

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<unsigned int, unsigned int> puu;
typedef pair<int, ll> pil;
typedef pair<int,double> pid;

const int INF = 0x3f3f3f3f;
const double eps = 1e-6;
const int LEN = 101;
int cnt, n, cut[LEN], low[LEN], dfn[LEN], vis[LEN];
vector<int> Map[LEN];

//割点模版初始化vis[] cut[]置0
//求割点若有重边需要判重
void dfs(int u, int fa){
    int v, i, son = 0;
    vis[u] = 1;
    dfn[u] = low[u] = cnt ++;
    for(i = 0; i < Map[u].size(); i ++){
        v = Map[u][i];
        if(vis[v] == 1 && v != fa)
            low[u] = min(low[u], dfn[v]);
        if(vis[v] == 0){
            dfs(v, u);
            son ++;
            low[u] = min(low[u], low[v]);
            if((fa < 0 && son > 1) || (fa > 0 && low[v] >= dfn[u]))
                cut[u] = true;
            //if(low[v] > dfn[u]){
            //   bridge[nbri][0] = u; bridge[nbri++][1] = v;   //边(i,j)是桥。
            //}
        }
    }
    vis[u] = 2;
}

int main()
{
//    freopen("in.txt", "r", stdin);

    int from, to;
    while(scanf("%d", &n)!=EOF && n){
        for(int i=0; i<LEN; i++)Map[i].clear();
        while(scanf("%d", &from) && from){
            while(getchar()!='
'){
                scanf("%d", &to);
                Map[from].PB(to);
                Map[to].PB(from);
            }
        }
        cnt = 0;
        memset(vis, 0, sizeof vis);
        memset(cut, 0, sizeof cut);
        dfs(1,-1);
        int ans = 0;
        for(int i=1; i<=n; i++)ans+=cut[i];
        printf("%d
", ans);
    }
    return 0;
}