POJ 1144 Network

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <vector>
 8 #include <queue>
 9 #include <cstdlib>
10 #include <string>
11 #include <set>
12 #include <stack>
13 #define LL long long
14 #define pii pair<int,int>
15 #define INF 0x3f3f3f3f
16 using namespace std;
17 const int maxn = 110;
18 int n,cnt,dfn[maxn],low[maxn];
19 vector<int>g[maxn];
20 bool iscut[maxn];
21 void tarjan(int u,int fa) {
22     dfn[u] = low[u] = ++cnt;
23     int v,son = 0;
24     for(v = 0; v < g[u].size(); v++) {
25         if(!dfn[g[u][v]]) {
26             son++;
27             tarjan(g[u][v],u);
28             if(low[u] > low[g[u][v]]) low[u] = low[g[u][v]];
29             if(low[g[u][v]] >= dfn[u]) iscut[u] = true;
30         } else if(g[u][v] != fa && low[u] > dfn[g[u][v]])
31             low[u] = dfn[g[u][v]];
32     }
33     if(fa < 0 && son == 1) iscut[u] = false;
34 }
35 int main() {
36     int u,v,ans;
37     while(scanf("%d",&n),n) {
38         for(int i = 0; i <= n; i++){
39             g[i].clear();
40             dfn[i] = low[i] = 0;
41             iscut[i] = false;
42         }
43         while(scanf("%d",&u),u) {
44             while(scanf("%d",&v)) {
45                 g[u].push_back(v);
46                 g[v].push_back(u);
47                 if(getchar() == ‘\n‘) break;
48             }
49         }
50         ans = cnt = 0;
51         tarjan(1,-1);
52         for(int i = 1; i <= n; i++)
53             ans += iscut[i];
54         printf("%d\n",ans);
55     }
56     return 0;
57 }