More is better（MST)（求无向图中最大集合元素个数）

#include<stdio.h>
#include<algorithm>
using namespace std;
int p[10000010] , rk[10000010] , maxn ;
int m ;

void init ()
{
    for (int i = 0 ; i <= 10000010 ; i++) {
        p[i] = i ;
        rk[i] = 1 ;
    }
    maxn = 0 ;
}

int find (int x)
{
    return x == p[x] ? x : p[x] = find (p[x]) ;
}

void Union (int x , int y)
{
    p[x] = y ;
    rk[y] += rk[x] ;
    maxn = max (maxn , rk[y]) ;
    rk[x] = 0 ;
}

int main ()
{
        //freopen ("a.txt" , "r" , stdin ) ;
        int x , y ;
        while (~ scanf ("%d" , &m) ) {
            init () ;
            for (int i = 0 ; i < m ; i++ ) {
                scanf ("%d%d" , &x , &y ) ;
                x = find (x) ;
                y = find (y) ;
                if (x != y)
                    Union ( x , y ) ;
            }
            if (maxn )
                printf ("%d\n" , maxn ) ;
            else
                printf ("1\n") ;
        }
        return 0 ;
}