一个无向图，n个顶点有n条边，输出一条可以删除的边，删除后使得图成为一棵树。可以使用并查集解决。

class Solution{public:    int father[1001];    void initfather()    {        for(int i=1; i<=1000; i++)            father[i]=i;    }    int findFather(int x)    {        if(father[x]!=x)            father[x] = findFather(father[x]);        return father[x];    }    void Merge(int x1, int x2)    {        int father_x1 = findFather(x1);        int father_x2 = findFather(x2);        if(father_x1 != father_x2)            father[father_x2] = father_x1;    }    vector
     
       findRedundantConnection(vector
      
       
        >& edges)    {        initfather();        vector
        
          res;        for(auto edge:edges)        {            int u = edge[0];            int v = edge[1];            if(findFather(u) == findFather(v))            {                res=edge;                break;            }            else                Merge(u,v);        }        return res;    }};