hdu杭电2120 Ice_cream's world I【并查集】

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

//这题是找环的个数

#include<stdio.h>
int per[100010];
int res=0;
int find(int x)
{
	if(x==per[x]) return x;
	return per[x]=find(per[x]);
}
void join(int x ,int y)
{
	int fx=find(x);
	int fy=find(y);
	if(fx!=fy)
	{
		per[fx]=fy;
	}
	else
	{
		res++;//找出有几块地即找几个环 
	}
}
int main()
{
	int a,b,m,n,i;
	while(~scanf("%d%d",&m,&n))
	{
		for(i=0;i<m;++i)
		{
			per[i]=i;
		}
		res=0;
		while(n--)
		{
			scanf("%d%d",&a,&b);
			join(a,b);
		}		
		printf("%d\n",res);
	}
	return 0;
}