POJ 1144--Network 【无向图中割点总数】

Description

Input

Output

Sample Input

5
5 1 2 3 4
0
6
2 1 3
5 4 6 2
0
0

Sample Output

1
2

Hint

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
#include <stack>
#define maxn 1000+10
#define maxm 2000000+10
using namespace std;

struct node {
    int u, v, next;
};

node edge[maxm];

int head[maxn], cnt;
bool is_cut[maxn];
int low[maxn], dfn[maxn];
int dfs_clock;

void init(){
    cnt = 0;
    memset(head, -1, sizeof(head));
}

void addedge(int u, int v){
    edge[cnt] = {u, v, head[u]};
    head[u] = cnt++;
    edge[cnt] = {v, u, head[v]};
    head[v] = cnt++;
}

int tarian(int u, int fa){
    low[u] = dfn[u] = ++dfs_clock;
    int son = 0;
    for(int i = head[u]; i != -1; i = edge[i].next){
        int v = edge[i].v;
        if(!dfn[v]){
            son++;
            low[v] = tarian(v, u);
            low[u] = min(low[u], low[v]);
            if(low[v] >= dfn[u])
                is_cut[u] = true;
        }
        else if(dfn[u] > dfn[v] && v != fa)
            low[u] = min(low[u], dfn[v]);
    }
    if(fa < 0 && son == 1) is_cut[u] = 0;
    if(fa < 0 && son > 1) is_cut[u] = true;
    return low[u];
}

void find(int l, int r){
    memset(low, 0, sizeof(low));
    memset(dfn, 0, sizeof(dfn));
    memset(is_cut, 0, sizeof(is_cut));
    for(int i = l; i <= r; ++i)
        if(!dfn[i]) tarian(i, -1);
}

int main (){
    int n;
    while(scanf("%d", &n), n){
        init();
        int u, v;
        while(scanf("%d", &u), u){
            while(getchar() != '\n'){
                scanf("%d", &v);
                addedge(u, v);
            }
        }
        find(1, n);
        int ans = 0;
        for(int i = 1; i <= n; ++i)
            if(is_cut[i])
                ans++;
        printf("%d\n", ans);
    }
    return 0;
}

POJ 1144--Network 【无向图中割点总数】

原文：http://blog.csdn.net/hpuhjh/article/details/47448477