Codeforces Round #254 (Div. 2) DZY Loves Chemistry【并查集基础】

 1 #include <stdio.h>
 2 #include <string.h>
 3 #include <stdlib.h>
 4 #include <math.h>
 5 #include <iostream>
 6 #include <algorithm>
 7 using namespace std;
 8 
 9 const int INF = 0x3f3f3f3f;
10 
11 int n, m, fa[100], x, y;
12 
13 int gf(int x) {
14     if (fa[x] != x)    fa[x] = gf(fa[x]);
15     return fa[x];
16 }
17 
18 int main() {
19     scanf("%d%d", &n, &m);
20     for (int i = 1; i <= n; i++)    fa[i] = i;
21     while (m--) {
22         scanf("%d%d", &x, &y);
23         fa[gf(x)] = gf(y);
24     }
25     long long ans = (1LL << n);
26     for (int i = 1; i <= n; i++)
27         if (gf(i) == i)    ans /= 2;
28     printf("%I64d\n", ans);
29 }