hdoj Work 5326 （并查集+技巧） 好题

Work

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1209    Accepted Submission(s): 737

Problem Description

It’s an interesting experience to move from ICPC to work, end my college life and start a brand new journey in company.
As is known to all, every stuff in a company has a title, everyone except the boss has a direct leader, and all the relationship forms a tree. If A’s title is higher than B(A is the direct or indirect leader of B), we call it A manages B.
Now, give you the relation of a company, can you calculate how many people manage k people.

Input

There are multiple test cases.
Each test case begins with two integers n and k, n indicates the number of stuff of the company.
Each of the following n-1 lines has two integers A and B, means A is the direct leader of B.

1 <= n <= 100 , 0 <= k < n
1 <= A, B <= n

Output

For each test case, output the answer as described above.

Sample Input

   
   
   
   

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

Sample Output

   
   
   
   

    
    
    
    2
   
   
   
   
   
   
   
   

    
    
    
     
   
   
   
   
   
   
   
   

    
    
    
    
#include<stdio.h>
#include<string.h>
int a[110];
int sum[110];
int find(int x)
{
	int r=x;
	while(r!=a[r])
		r=a[r];
	int i=x,j;
	while(i!=r)
	{
		j=a[i];
		sum[j]++;
		i=j;
	}
	return r;
}
int main()
{
	int n,m,i,j,x,y;
	while(scanf("%d%d",&n,&m)!=EOF)
	{
		memset(sum,0,sizeof(sum));
		int nn=n-1;
		for(i=1;i<=n;i++)
			a[i]=i;
		while(nn--)
		{
			scanf("%d%d",&x,&y);
			if(x!=y)
				a[y]=x;
		}
		for(i=1;i<=n;i++)
			find(i);
		int cnt=0;
		for(i=1;i<=n;i++)
		{
			if(sum[i]==m)
				cnt++;
		}
		printf("%d\n",cnt);
	}
	return 0;
}