lightoj 1026 无向图 求桥

题目链接：http://lightoj.com/volume_showproblem.php?problem=1026

#include<cstdio>
#include<cstring>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<queue>
#include<vector>
using namespace std;
const int maxn = 10050;
const int INF = 0x3f3f3f;vector<int> G[maxn];
int pre[maxn],dfs_clock,low[maxn];struct ANS{int l,r;bool operator < (const ANS& a) const{return l < a.l || (l == a.l && r < a.r);    //排序被坑了，WA了好几次啊，没想后面的情况。
    }
}ans[maxn];
int cnt;
int n;void tarjan(int u,int fa){low[u] = pre[u] = dfs_clock++;for(int i=0;i<G[u].size();i++){int v = G[u][i];if(v == fa)  continue;if(!pre[v]){tarjan(v,u);low[u] = min(low[u],low[v]);if(low[v] > pre[u]){ans[cnt].l = min(u,v);ans[cnt].r = max(u,v);cnt++;}}elselow[u] = min(low[u],pre[v]);  }
}void init(){cnt = 0;dfs_clock = 1;memset(pre,0,sizeof(pre));for(int i=0;i<n;i++)  G[i].clear();
}
int main()
{freopen("E:\\acm\\input.txt","r",stdin);int T;cin>>T;for(int t=1;t<=T;t++){scanf("%d",&n);init();for(int i=0;i<n;i++){int u,m;scanf("%d (%d)",&u,&m);for(int j=1;j<=m;j++){int v;scanf("%d",&v);G[u].push_back(v);}}for(int i=0;i<n;i++){if(!pre[i]){tarjan(i,-1);}}printf("Case %d:\n",t);printf("%d critical links\n",cnt);sort(ans,ans+cnt);for(int i=0;i<cnt;i++){printf("%d - %d\n",ans[i].l,ans[i].r);}}
}