小希的迷宫(hdu 1272)

#include<iostream>
#include<stdio.h>
#include<math.h>
#include<string.h>
#include<vector>
#include<list>
#include<algorithm>
using namespace std;
int a[100000];
int solve(int x,int y);
int find(int x);
int book[100000];
int main(){
int x,y;
while(1){
int s = 0;
int num = -1;
memset(a,0,sizeof(a));
memset(book,0,sizeof(book));
while(1){
scanf("%d%d",&x,&y);
if(x==-1&&y==-1)	return 0;
num = max(num,max(x,y));
book[x] = book[y] = 1;
if(x==0&&y==0)	break;
else{
if(s)	continue;
s = solve(x,y);
}
}
if(s)	printf("No\n");
else{
for(int i=1;i<=num;i++){
if(book[i]&&a[i]==0)	s++;
}
if(s>1)	printf("No\n");
else printf("Yes\n");
}
}
return 0;
}
int solve(int x,int y){
int c = find(x);
int b = find(y);
if(c==b)	return 1;
else a[c] = b;
return 0;
}
int find(int x){
if(a[x]==0)	return x;
else{
a[x] = find(a[x]);
return a[x];
}
}