hdu 1232 畅通工程（最小生成树）

 1 #include<iostream>
 2 #include<stdio.h>
 3 #include<string.h>
 4 #include<stdlib.h>
 5 #include<math.h>
 6 #include<algorithm>
 7 #define LL long long
 8 #define mod 1e9 + 7
 9 const int M = 1005;
10 
11 using namespace std;
12 
13 struct node{
14     int x;
15     int y;
16 }a[M * M >> 1];
17 
18 int cun[M];
19 
20 int find(int x)
21 {
22     return cun[x] == x ? x : cun[x] = find(cun[x]);
23 }
24 
25 void shu(int x, int y)
26 {
27     int p = find(x);
28     int q = find(y);
29     cun[p] = q;
30 }
31 
32 int main()
33 {
34     int n, m;
35     while( cin >> n )
36     {
37         if(n == 0)
38             break;
39         cin >> m;
40         for(int i = 1; i <= m; ++i)
41             scanf("%d%d",&a[i].x,&a[i].y);
42         for(int i = 1; i <= n; ++i)
43             cun[i] = i;
44         int cnt = 1;
45         for(int i = 1; i <= m; ++i)
46         {
47             if(find(a[i].x) != find(a[i].y))
48             {
49                 shu(a[i].x,a[i].y);
50                 cnt++;
51             }
52         }
53         cout << n - cnt << endl;
54     }
55     return 0;
56 }