hdu1856More is better 并查集基础

More is better

Time Limit: 5000/1000 MS (Java/Others)    Memory Limit: 327680/102400 K (Java/Others)
Total Submission(s): 2618    Accepted Submission(s): 1006

Problem Description

Mr Wang wants some boys to help him with a project. Because the project is rather complex, the more boys come, the better it will be. Of course there are certain requirements.

Mr Wang selected a room big enough to hold the boys. The boy who are not been chosen has to leave the room immediately. There are 10000000 boys in the room numbered from 1 to 10000000 at the very beginning. After Mr Wang's selection any two of them who are still in this room should be friends (direct or indirect), or there is only one boy left. Given all the direct friend-pairs, you should decide the best way.

 

 

Input

The first line of the input contains an integer n (0 ≤ n ≤ 100 000) - the number of direct friend-pairs. The following n lines each contains a pair of numbers A and B separated by a single space that suggests A and B are direct friends. (A ≠ B, 1 ≤ A, B ≤ 10000000)

 

 

Output

The output in one line contains exactly one integer equals to the maximum number of boys Mr Wang may keep.

 

 

Sample Input

   
   
   
   

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

 

 

Sample Output

   
   
   
   

    
    
    
    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. 
    
这一题告诉我们如何统计集合中的元素个数，这里的rank[i],表示的不再是i结点的深度，而是i所在集合中的元素个数
   
   
   
   
   
   
   
   

    
    
    
    因此，与模板有些不同
   
   
   
   
   
   
   
   

    
    
    #include<stdio.h>
int parent[10000005];
int rank[10000005];
void Create(int i)
{
    parent[i]=i;
    rank[i]=1;//统计这个集合里有多少个元素
}
int Find(int i)
{
    int u=i;
    while(u!=parent[u])
    {
        u=parent[u];
    }
    while(i!=u)
    {
        int t=parent[i];
        parent[i]=u;
        i=t;
    }
    return u;
}
void Union(int a,int b)
{
    int l1=Find(a);
    int l2=Find(b);
    if(l1==l2) return;//a,b已在同一集合，重点啊！！！！
    if(rank[l1]>rank[l2])
    {
        parent[l2]=l1;
        rank[l1]=rank[l2]+rank[l1];
    }
    else
    {
        //if(rank[l1]==rank[l2])
        //rank[l2]++;
        parent[l1]=l2;
        rank[l2]=rank[l2]+rank[l1];
    }
}
int main()
{
    int n,a,b;
    while(scanf("%d",&n)!=EOF)
    {
        if(n==0) {printf("1/n");continue;}
        for(int i=1;i<=10000000;i++)
        Create(i);
        for(int i=1;i<=n;i++)
        {
            scanf("%d%d",&a,&b);
            Union(a,b);
            //printf("%d %d %d %d/n",a,rank[a],b,rank[b]);
        }
        int max=0;
        for(int i=1;i<=10000000;i++)
        {
            if(rank[i]>=max) max=rank[i];
        }
        printf("%d/n",max);
    }
    return 0;
}