hdu-1213 How Many Tables

#include<stdio.h>
#include<string.h>
#include<algorithm>
using namespace std;
int pre[1200];
int mark[1300];
int find(int x){
   return pre[x]==x?x:find(pre[x]);    
}
int main(){
   int T;
   int n,m;
   int a,b,i,j,k,t;
   scanf("%d",&T);
   while(T--){
       memset(pre,0,sizeof(pre));
       memset(mark,0,sizeof(mark));
       scanf("%d%d",&n,&m);
       int fx,fy;
       for(i=0;i<=n;i++){
          pre[i]=i;
          mark[i]=i;
        }
        int sum=n;
       for(i=0;i<m;i++){
         scanf("%d %d",&a,&b);
         fx=find(a);
         fy=find(b);                
         if(fx!=fy){
           sum-=1;
           pre[fx]=fy;
         }
       }
      printf("%d\n",sum);            
   }    
return 0;
}