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并查集最大秩

#include<stdio.h>
#include<iostream>
#include<math.h>
#include<stdlib.h>
#include<ctype.h>
#include<algorithm>
#include<vector>
#include<string.h>
#include<queue>
#include<stack>
#include<set>
#include<map>
#include<sstream>
#include<time.h>
#include<utility> 
#include<malloc.h> 
#include<stdexcept>

using namespace std;

int p[10000010];
int r[10000010];
int maxx ;

int find(int x)
{
    if (x==p[x])
        return x;
    else
        return find ( p[x] );
}

void un (int a,int b)
{
    int fa = find (p[a]);
    int fb = find (p[b]);
    if(fa == fb )
        return ;

    if (r[fa]>r[fb])
        {
            p[fb]=fa;
            r[fa]+=r[fb];
            if (maxx < r[fa] )
                maxx = r[fa];
        }
    else
        {
            p[fa]=fb;
            r[fb]+=r[fa];
            if(maxx < r[fb])
                maxx = r[fb];
        }

}

int main ()
{
    int m;
    while (scanf ("%d",&m) != EOF )
    {
        for (int i=1;i<=10000000;i++)
        {
            p[i]=i;
            r[i]=1;
        }
        int a,b;
        maxx = 1;

        for (int i=0;i<m;i++)
        {
            scanf ("%d%d",&a,&b);
            un(a,b);
        }

        printf("%d\n",maxx);

    }
    return 0;
}