按秩合并 HDU 1232

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
const int maxn=1000+10;
int n,m;
int cnt;
int f[maxn],size[maxn];
int find(int x){
    return x==f[x] ? x : f[x]=find(f[x]);
}
void lunion(int x,int y){
    int fx=find(x),fy=find(y);
    if(fx==fy)
        return;
    if(size[x]>=size[y]){
        f[fy]=fx,size[x]+=size[y];
        return;
    }
    f[fx]=fy,size[y]+=size[x];
    return;
}
int main(){
    while(scanf("%d",&n)&&n!=0){
        scanf("%d",&m);
        cnt=0;
        for(int i=1;i<=n;i++)
            f[i]=i,size[i]=1;
        int x,y; 
        for(int i=1;i<=m;i++)
            scanf("%d%d",&x,&y),lunion(x,y);
        for(int i=1;i<=n;i++)
            if(f[i]==i)
                cnt++;
        printf("%d\n",cnt-1);
    }
    return 0;
}