Ice_cream's world I

Problem Description

ice_cream's world is a rich country, it has many fertile lands. Today, the queen of ice_cream wants award land to diligent ACMers. So there are some watchtowers are set up, and wall between watchtowers be build, in order to partition the ice_cream’s world. But how many ACMers at most can be awarded by the queen is a big problem. One wall-surrounded land must be given to only one ACMer and no walls are crossed, if you can help the queen solve this problem, you will be get a land.

 

Input

In the case, first two integers N, M (N<=1000, M<=10000) is represent the number of watchtower and the number of wall. The watchtower numbered from 0 to N-1. Next following M lines, every line contain two integers A, B mean between A and B has a wall(A and B are distinct). Terminate by end of file.

 

Output

Output the maximum number of ACMers who will be awarded.
One answer one line.

 

Sample Input

8 10 0 1 1 2 1 3 2 4 3 4 0 5 5 6 6 7 3 6 4 7

 

Sample Output

3

 

       很简单的题     查找环的个数

#include<stdio.h>
#include<cstring>
int pre[1001];
int find(int p)  //路径压缩 
{  
    int r=p;  
    int t;  
    while(p!=pre[p])  
    p=pre[p];  
    while(r!=p)  
    {  
        t=pre[r];  
        pre[r]=p;  
        r=t;  
    }  
    return p;  
} 
void merge(int x,int y)
{
	int fx=find(x);
	int fy=find(y);
	if(fx!=fy)
	{
		pre[fx]=fy;
	}
}
int main()
{
	int m,n,a,b,i,flog,k,f;	
		while(scanf("%d%d",&a,&b)!=EOF)
		{
			for(int i=0;i<a;i++)
		    {
			pre[i]=i;
		     }
	        flog=0;
	       while(b--)
		   {
		   	scanf("%d%d",&n,&m);
	         if(find(n)==find(m))//判断是否成环 
	         flog++;
	         merge(n,m);
			} 
		   printf("%d\n",flog);
		}
	return 0;
 }