hdu 1271 简单并查集

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int maxn=100002;
int father[maxn],vis[maxn],n,m,ans,t,tmp;
int Find(int x)
{
    if(father[x]==x)return x;
    return father[x]=Find(father[x]);
}
void Union(int x,int y)
{
    int xx=Find(x);
    int yy=Find(y);
    if(xx!=yy)
    {
        if(xx>yy)swap(xx,yy);
        father[yy]=xx;
    }
    if(xx==yy)//存在回路
        tmp++;
}
int main()
{
    int i,j,a,b,flag=1,Max=maxn;
    while(flag)
    {
        memset(vis,0,sizeof(vis));
        for(i=1; i<=100000; i++)
        {
            father[i]=i;
        }
        tmp=0;Max=1;
        while(scanf("%d%d",&a,&b),(a||b))
        {
            if(a==-1&&b==-1)
            {
                flag=0;
                break;
            }
            vis[a]=1;
            vis[b]=1;
            Max=max(Max,max(a,b));
            Union(a,b);
        }
        if(!flag)continue;
        for(i=1; i<=Max; i++)
        {
            if(vis[i]&&father[i]==i)tmp++;
        }
        if(tmp<=1) printf("Yes\n");
        else printf("No\n");
    }
    return 0;
}