POJ 2117 Electricity

 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 = 10100;
18 int p,c;
19 int dfn[maxn],low[maxn],cut[maxn],vis[maxn],cnt;
20 vector<int>g[maxn];
21 void tarjan(int u,int fa){
22     dfn[u] = low[u] = ++cnt;
23     int son = 0;
24     vis[u] = 1;
25     for(int i = 0; i < g[u].size(); i++){
26         if(!vis[g[u][i]]){
27             tarjan(g[u][i],u);
28             son++;
29             low[u] = min(low[u],low[g[u][i]]);
30             if(fa == -1 && son > 1 || fa != -1 && dfn[u] <= low[g[u][i]]) cut[u]++;
31         }else if(g[u][i] != fa && vis[g[u][i]] == 1) low[u] = min(low[u],dfn[g[u][i]]);
32     }
33     vis[u] = 2;
34 }
35 int main() {
36     int i,u,v,ans,sum;
37     while(scanf("%d %d",&p,&c),p||c){
38         if(!c){printf("%d\n",p-1);continue;}
39         for(i = 0; i <= p; i++){
40             g[i].clear();
41             vis[i] = 0;
42             dfn[i] = 0;
43             cut[i] = 0;
44         }
45         for(i = 0; i < c; i++){
46             scanf("%d %d",&u,&v);
47             g[u].push_back(v);
48             g[v].push_back(u);
49         }
50         ans = sum = cnt = 0;
51         for(i = 0; i < p; i++){
52             if(!vis[i]){tarjan(i,-1);sum++;}
53             if(cut[i] > ans) {ans = cut[i];}
54         }
55         printf("%d\n",ans+sum);
56     }
57     return 0;
58 }