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#include<stdio.h>  
#include<string.h>

 
int ff[100005];//ff[x]表示x的父节点 
int ss[100005];//
int x[100005],y[100005];

void ii(int n)    //初始化   
{  
    for(int i=1;i<=n;i++) 
	{ 
        ff[i]=i;     
        ss[i]=1;   //
    } 
}  
  
int dd(int x)    //带路径压缩的查找
{  
    if(x!=ff[x])
		ff[x]=dd(ff[x]);
	return ff[x];	
} 

void cc(int a,int b)    //合并
{  
    ff[a] = b;
    ss[b] += ss[a];
}  

int main()  
{  
    int i,m,a,b,t,k,j,N;
	int count,max=0;
    while(~scanf("%d",&N)) 
	{
       for(i=1;i<=N;i++)
	   {
            scanf("%d%d",&x[i],&y[i]);
			if(x[i]>max) max = x[i];  
            if(y[i]>max) max = y[i];  
	   }
	   ii(max);
	   for(i=1;i<=N;i++)
	   { 
		   int ta=dd(x[i]);  
           int tb=dd(y[i]); 
		   if(ta!=tb)
		     cc(ta,tb);
	   }
	   int ans=0;
	   for (i=1;i<=max;i++)
	   {
		   if(ss[i] > ans)
			   ans = ss[i];
	   }
        printf("%d\n",ans);
    }  
    return 0;  
} 

并查集的运用

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.
 
 

HDU 1856 More is better (并查集)

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原文地址：http://blog.csdn.net/xinwen1995/article/details/45918929