连通图（sf14b）

解题思路:

注意事项:

参考代码:

#include<bits/stdc++.h>

using namespace std;

const int N=100005;

int father[N];

//找根节点

int Find(int x)

{

        if(x==father[x]) return x;

        else return father[x]=Find(father[x]);//压缩路径 

} 

//合并

void Union(int a,int b)

{

        int FA=Find(a);

        int FB=Find(b);

        if(FA!=FB)

            father[FA]=FB;

} 

int main()

{

        int n,m;

        while(cin>>n>>m)

        {

            if(n==0) break;

             //初始化 

             for(int i=1;i<=n;i++)

             father[i]=i;

             //处理m条边

             int x,y;

             while(m--)

             {

                     cin>>x>>y;

                     Union(x,y);

             } 

             //判断是否联通

             int r1,r2;

             cin>>r1>>r2;

             if(Find(r1)==Find(r2)) cout<<"Yes"<<endl;

             else                                     cout<<"No"<<endl; 

             }

}