HDU 1272 小希的迷宫

#include<bits/stdc++.h>
using namespace std;
const int maxx=100010;
int i,a,b,q,p,l,t,ok,fat[maxx],c[maxx];
int find(int x){
if(fat[x]!=x)fat[x]=find(fat[x]);
return fat[x];
}
int main(){
while(1){
ok=1;
for(i=1;i<=100001;i++)
fat[i]=i;
memset(c,0,sizeof(c));
while(1){
scanf("%d%d",&a,&b);
if(a==-1&&b==-1)return 0;
if(a==0&&b==0)break;
c[a]=1;
c[b]=1;
q=find(a);
p=find(b);
if(q==p)ok=0;
fat[q]=p;
}
l=0;
for(i=1;i<=100001;i++)
if(c[i]){
t=find(i);
if(l==0)l=t;
if(l!=t){
ok=0;
break;
}
}
if(ok==1)printf("Yes\n");
else printf("No\n");
}
return 0;
}