题目大意：给出一个连通图，求再一个边后，剩余的最少桥数。

题目思路：首先进行缩点得到重构后的图，求出重构后树的直径（通过两次BFS求出相距最远的两点间的距离）,ans=重构图边数-树的直径

//#pragma comment(linker, "/STACK:102400000,102400000")#include
      
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              #define MAXSIZE 200005#define LL long longusing namespace std;vector
              
               
                 >G;vector
                
                 
                   >G2;int vis[MAXSIZE],low[MAXSIZE],dfn[MAXSIZE],pre[MAXSIZE],k,Time,n,m,ans,link;int dist[MAXSIZE],belong[MAXSIZE],step[MAXSIZE],Stuck[MAXSIZE],block;void Tarjan(int u,int fa){ low[u]=dfn[u]=++Time; pre[u]=fa; Stuck[k++]=u; int v,len=G[u].size(),op=0; for(int i=0;i
                  

Q; memset(step,-1,sizeof(step)); step[s]=0; Q.push(s); while(!Q.empty()) { now=Q.front(); Q.pop(); int len=G2[now].size(); for(int i=0;i