hdu 1272 小希的迷宫(并查集 最小生成树)

http://acm.hdu.edu.cn/showproblem.php?pid=1272

这题要求任意两个房间都相通又不能有环 

即通过并查集求出是否构成最小生成树

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
#define maxn 100000
int fa[maxn+10];
int num[maxn+10];
int vis[maxn+10];
int ans,coun;
int find(int x)
{
    return fa[x]=(x==fa[x]?x:find(fa[x]));
}
void fun(int x,int y)
{
    int fx=find(x);
    int fy=find(y);
    if(fx==fy)
    {
        ans=0;
        return ;
    }
    if(vis[x]==0) {vis[x]++;coun++;}
    if(vis[y]==0) {vis[y]++;coun++;}
    fa[fx]=fa[fy];
    num[fy]+=num[fx];
    if(num[fy]>ans) ans=num[fy];
}
int main()
{
    int n;
    int l,r;
    int i,j,k;
    while(scanf("%d%d",&l,&r)!=EOF)
    {
        if(l==0&&r==0) {printf("Yes
"); continue;}
        if(l==-1&&r==-1) break;
        ans=1;
        coun=0;
        for(i=0;i<=maxn;i++) {fa[i]=i;num[i]=1;}
        memset(vis,0,sizeof(vis));
        while(l!=0||r!=0)
        {
            if(ans)
            fun(l,r);
            scanf("%d%d",&l,&r);
        }
        if(ans==coun) printf("Yes
");
        else printf("No
");
    }
    return 0;
}