題意：問給出的望塔之間的建造了圍墻，將土地分成了幾份

思路：用并查集判環，若有圍墻相接的瞭望塔，有相同的父根，則存在環

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 #include<iostream> #include<string.h> using namespace std; int m,n,dp[1010]; int f(int xx) {if(xx==dp[xx])return xx;elsereturn f(dp[xx]); } int dfs(int x,int y) {int a=f(x);int b=f(y);if(a!=b){dp[b]=a;return 0;}elsereturn 1; } int main() {while(cin>>m>>n){int sum=0;for(int i=0; i<m; i++)dp[i]=i;while(n--){int t1,t2;cin>>t1>>t2;sum+=dfs(t1,t2);}cout<<sum<<endl;}return 0; }

?

總結

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