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

8 100 11 21 32 43 40 55 66 73 64 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;}