HDU1856 More is better(并查集)

#include<stdio.h>
#define N 10000000
int father
,num
;
void initial()
{
    int i;
    for(i=1;i<=N;i++)
    {
        father[i]=i;
        num[i]=1;
    }
}
int find(int x)
{
    if(father[x]!=x)
        father[x]=find(father[x]);
    return father[x];
}
void merge(int a,int b){
    int p=find(a);
    int q=find(b);
    if(p!=q)
    {
        father[p]=q;
        num[q]+=num[p];
    }
}
int main()
{
    int n,a,b,i,sum,max;
    while(~scanf("%d",&n)){
        if(n==0){
            printf("1\n");
            continue;
        }
        max=0;
        initial();
        for(i=0;i<n;i++)
        {
            scanf("%d%d",&a,&b);
            if(a>max) max=a;
            if(b>max) max=b;
            merge(a,b);
        }
        int MAX=0;
        for(int i=1;i<=max;i++)
            if(num[i]>MAX) MAX=num[i];
        printf("%d\n",MAX);
    }
}