HDU 1272 小希的迷宫

1 1 0 0
0 0
1 2 3 4 0 0
1 2 2 3 3 4 0 0
1 3 5 3 0 0
-1 -1

No
Yes
No
Yes
Yes

#include <stdio.h>

int fa[100005];  //父亲数组
int visit[100005];  //表示是否被连接过
int load(){
int i;
for(i = 0; i<100005; i++)
fa[i] = i;
}

int find(int x){
if(x!=fa[x])
fa[x] = find(fa[x]);
return fa[x];
}

int main(){
int m, n;
int x, y, fx, fy;
int i, flag, flag1, count;

while(scanf("%d%d", &m, &n)){
flag = 0;
count = 0;
flag1 = 0;
if(m==-1&&n==-1)    break;
else if(m==0&&n==0);
else {
load();
memset(visit, 0, sizeof(visit));
fa[m] = n;
visit[m] = 1;
visit
= 1;
if(m==n) flag = 1;
while(scanf("%d%d", &x,&y),x&&y){
fx = find(x);
fy = find(y);
visit[x] = 1;
visit[y] = 1;
if(fx==fy) flag = 1;
else fa[fx] = fy;
}
}
for(i = 0; i<100005; i++){
if(visit[i]&&fa[i]==i)
flag1++;
if(visit[i])
count++;
}

if(count==0)    printf("Yes\n");  //0 0的测试数据
else if(!flag&&flag1==1)   printf("Yes\n"); //没有回环并且只有一棵树
else    printf("No\n");
}
return 0;
}