ZOJ 1311 Network 割顶

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裸的连通图求割点
#include <cstdio>#include <algorithm>#include <cstring>#include <iostream>#include <vector>using namespace std;#define N 103vector<int> g[N];int n, low[N], dfn[N], f[N];bool vis[N];void dfs(int u, int depth, const int &root) {    dfn[u] = low[u] = depth;    vis[u] = true;    int cnt = 0;    for (int i=0; i<g[u].size(); i++) {        int v = g[u][i];        if (!vis[v]) {            cnt++;            dfs(v, depth+1, root);            low[u] = min(low[u], low[v]);            if (u!=root && low[v]>=dfn[u]) f[u]++;            if (u==root && cnt>=2) f[u]++;        } else low[u] = min(low[u], dfn[v]);    }}int main() {    int a, b, l;    char s[1000];    while (scanf("%d", &n) == 1 && n) {        for (int i=0; i<=n; i++) g[i].clear();        while (scanf(" %d", &a) == 1 && a) {            b = 0;            gets(s);            l = strlen(s);            for (int i=0; i<l; i++) {                if (s[i] == ' ') {                    if (b) {                        g[a].push_back(b);                        g[b].push_back(a);                        b = 0;                    }                } else b = b*10 + s[i]-'0';            }            if (b) { g[a].push_back(b); g[b].push_back(a); }        }        memset(f, 0, sizeof(f));        memset(vis, false, sizeof(vis));        dfs(1, 1, 1);        int ans = 0;        for (int i=1; i<=n; i++) if (f[i] >= 1) ans++;        printf("%d\n", ans);    }    return 0;}