小鑫的城堡(sdut_2798)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int a[112345];
int hash[112345];
int find(int x)
{
while(x != a[x]){
x = a[x];
}
return x;
}
void merge(int u, int v)
{
int f1, f2;
f1 = find(u);
f2 = find(v);
if(f1 != f2){
a[f1] = f2;
}
}
int main()
{
int m;
while(~scanf("%d", &m)){
memset(hash,0,sizeof(hash));
int i;
for(i = 1;i <= 100000;i++){
a[i] = i;
}
int flag = 1;
int t = 0;
int u, v;
for(i = 0;i < m;i++){
scanf("%d %d", &u, &v);
if(hash[u] == 0){
hash[u] = 1;
t++;
}
if(hash[v] == 0){
hash[v] = 1;
t++;
}
if(find(u) == find(v)){
flag = 0;
}
t--;
merge(u,v);
}
if(t == 1 && flag == 1){
printf("Yes\n");
}else {
printf("No\n");
}
}

return 0;
}