【模板】并查集

唔...有空补

#include<bits/stdc++.h>
using namespace std;
int find (int x){
    int r=x;
    while (pre[r]!=r) {
        r=pre[r];
    }
    int i=x,j;
    while (i!=r) {
        j=pre[i];
        pre[i]=r;
        i=j;
    }
    return r;
}
void join (int x,int y){
    int a=find(x);
    int b=find(y);
    if(a!=b){
        pre[a]=b;
    }
}
int main(){
    
    return 0;
}