Codeforces Round #254 (Div. 2) B. DZY Loves Chemistry （并查集）

 1 #include <iostream>
 2 #include <cstring>
 3 #include <queue>
 4 #include <cmath>
 5 #include <cstdio>
 6 #include <algorithm>
 7 #define LL long long
 8 using namespace std;
 9 const int maxn = 50 + 10;
10 int n, m, bin[maxn], f[maxn], cou;
11 int find(int x)
12 {
13     return bin[x]==x?x:(bin[x]=find(bin[x]));
14 }
15 void merge(int x, int y)
16 {
17     int fx = find(x);
18     int fy = find(y);
19     if(fx != fy)
20     {
21         bin[fx] = fy;
22         cou ++;
23     }
24 }
25 int main()
26 {
27     int i, x, y;
28     LL ans;
29     while(~scanf("%d%d", &n, &m))
30     {
31         cou = 0;
32         for(i = 1; i <= n; i++)
33         bin[i] = i;
34         while(m--)
35         {
36             cin>>x>>y;
37             merge(x, y);
38         }
39         ans = pow(2, cou);
40         cout<<ans<<endl;
41     }
42     return 0;
43 }