poj2524 Ubiquitous Religions

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdio>
 4 using namespace std;
 5 
 6 const int N = 50000 + 10;
 7 int p[N];
 8 
 9 void make_set(int n)
10 {
11     for (int i = 1;i <= n;i++)
12         p[i] = -1;
13 }
14 
15 int find_root(int i)
16 {
17     if (p[i] == -1)
18         return i;
19     else
20     {
21         int temp = find_root(p[i]);        //路径压缩
22         p[i] = temp;
23         return temp;
24     }
25 }
26 
27 void union_set(int a, int b)
28 {
29     int ra = find_root(a);
30     int rb = find_root(b);
31     if (ra != rb)
32         p[ra] = rb;
33 }
34 
35 int main()
36 {
37     //freopen("poj2524.txt", "r", stdin);
38     int n, m;
39     int cnt = 0;
40     while (scanf("%d%d", &n, &m) == 2 && n)
41     {
42         make_set(n);
43         int a, b;
44         for (int i = 0; i < m; i++)
45         {
46             scanf("%d%d", &a, &b);
47             union_set(a, b);
48         }
49         int ans = 0;
50         for (int i = 1;i <= n;i++)
51             if (p[i] == -1) ans++;
52         printf("Case %d: %d\n", ++cnt, ans);
53     }
54     return 0;
55 }