1076: [SCOI2008]奖励关

 1 #include<cstdio>
 2 #include<algorithm>
 3 #include<cstring>
 4 #include<iostream>
 5 #include<cmath>
 6     
 7 using namespace std;
 8     
 9 double dp[110][50010];
10 int b[20],w[20];
11     
12 inline int read() {
13     int x = 0,f = 1; char ch = getchar();
14     for (; !isdigit(ch); ch=getchar()) if(ch==‘-‘) f=-1;
15     for (; isdigit(ch); ch=getchar()) x = x*10+ch-‘0‘;
16     return x * f;
17 }
18     
19 int main() {
20     int m = read(),n = read();
21     for (int i=1; i<=n; ++i) {
22         w[i] = read();
23         int tmp = 0,a = read();
24         while (a) {
25             tmp |= (1<<(a-1));
26             a = read();
27         }
28         b[i] = tmp;
29     }
30      
31     int t = (1 << n) - 1;
32     for (int i=m; i>=1; --i) {
33         for (int s=t; s>=0; --s) {
34             for (int k=1; k<=n; ++k) {
35                 if ((b[k]&s)^b[k]) dp[i][s] += dp[i+1][s];
36                 else dp[i][s] += max(dp[i+1][s],dp[i+1][s|(1<<(k-1))]+w[k]);
37             }
38             dp[i][s] /= double(n);
39         }
40     }
41     printf("%.6lf",dp[1][0]);
42     return 0;
43 }