【HDOJ】4587 TWO NODES

Tarjan解无向图的割点和桥，参考白书。

 /* 4587 */
 #include <iostream>
 #include <vector>
 #include <algorithm>
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>
 using namespace std;

 #define MAXN 5005

 vector<int> vc[MAXN];
 int dfs_clock;
 int cnt[MAXN];
 int pre[MAXN];
 int n, m, cur;

 int Tarjan(int u, int fa) {
     int i, j, k, v;
     int lowu, lowv;
     int child = ;

     lowu = pre[u] = ++dfs_clock;
     for (i=; i<vc[u].size(); ++i) {
         v = vc[u][i];
         if (v==fa || v==cur)
             continue;
         if (!pre[v]) {
             ++child;
             lowv = Tarjan(v, u);
             lowu = min(lowu, lowv);
             if (lowv >= pre[u])
                 ++cnt[u];
         } else if (pre[v] < pre[u])
             lowu = min(lowu, pre[v]);
     }
     if (fa < )
         cnt[u] = child - ;
     return lowu;
 }

 void init() {
     dfs_clock = ;
     memset(cnt, , sizeof(int)*n);
     memset(pre, , sizeof(int)*n);
 }

 int main() {
     int i, j, k;
     int ans;

     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
     #endif

     while (scanf("%d %d", &n, &m)!=EOF) {
         for (i=; i<n; ++i)
             vc[i].clear();
         while (m--) {
             scanf("%d %d", &i, &j);
             vc[i].push_back(j);
             vc[j].push_back(i);
         }
         ans = ;
         for (cur=; cur<n; ++cur) {
             init();
             k = ;
             for (i=; i<n; ++i) {
                 if (i!=cur && !pre[i]) {
                     ++k;
                     Tarjan(i, -);
                 }
             }
             for (i=; i<n; ++i)
                 if (i!=cur)
                     ans = max(ans, k+cnt[i]);
         }
         printf("%d\n", ans);
     }

     return ;
 }