More is better hdu1856 并查集

http://acm.hdu.edu.cn/showproblem.php?pid=1856

题意：老师想从10000000里面找尽可能多的学生帮他做项目，条件是这些人必须都认识。给n个关系，求最多有多少个人能帮助老师做项目。

因为数据量较大，如果不进行数据压缩的话就过不去。

#include <iostream>using namespace std;#define N 10000005int boy[N];int findfather(int n){if (boy[n]<0)return n;boy[n]=findfather(boy[n]);return boy[n];}int main(){#ifndef ONLINE_JUDGEfreopen("1856in.txt","r",stdin);#endifint n,a,b,i,min;while (scanf("%d",&n)!=EOF){for (i=1;i<N;i++)boy[i]=-1;for (i=0;i<n;i++){scanf("%d%d",&a,&b);a=findfather(a);b=findfather(b);if (a!=b){if (boy[a]<=boy[b]){boy[a]+=boy[b];boy[b]=a;}else {boy[b]+=boy[a];boy[a]=b;}}}min=0;for (i=1;i<N;i++)if (boy[i]<min)min=boy[i];printf("%d\n",-min);}return 0;}