标签：hdu   并查集   1856   more is better   

More is better

4
1 2
3 4
5 6
1 6
4
1 2
3 4
5 6
7 8

4
2

Hint
A and B are friends(direct or indirect), B and C are friends(direct or indirect), 
then A and C are also friends(indirect).

 In the first sample {1,2,5,6} is the result.
In the second sample {1,2},{3,4},{5,6},{7,8} are four kinds of answers.
 
 

这也是一个并查序的问题，问的是friends最多有多少个，其实就是计算ranks的最大值。

#include<iostream>
#include<stdio.h>
using namespace std;
#define M 10000010
int ranks[M];//一开始还以为空间不够，结果这题给的空间很大
int pre[M];
int _find(int node)
{
    int t=node;
    if(node==pre[node])return node;
    else
        return pre[node]=_find(pre[node]);
}
int _union(int a,int b)
{
    int p=_find(a);
    int q=_find(b);
    if(p!=q)
    {
        if(ranks[p]<ranks[q]){pre[p]=q;
            ranks[q]+=ranks[p];}
            else{
                pre[q]=p;
                ranks[p]+=ranks[q];
            }
    }
}
int main(int argc, char *argv[])
{
    //freopen("1856.in","r",stdin);
    int n;
    int a,b;
    while(scanf("%d",&n)!=EOF)
    {
        for(int i=1;i<M;++i)
        {
            pre[i]=i;
            ranks[i]=1;
        }
        while(n--)
        {
            scanf("%d %d",&a,&b);
            _union(a , b);
        }
        int max=0;
        for(int i=1;i<M;++i)
        {
            if(ranks[i]>max)max=ranks[i];
        }
        printf("%d\n",max);

    }
    return 0;
}

HDU 1856 More is better （并查集）

标签：hdu   并查集   1856   more is better   

原文地址：http://blog.csdn.net/wdkirchhoff/article/details/41758861