bzoj 1076

 1 #include<bits/stdc++.h>
 2 #define inc(i,l,r) for(int i=l;i<=r;i++)
 3 #define dec(i,l,r) for(int i=l;i>=r;i--)
 4 #define link(x) for(edge *j=h[x];j;j=j->next)
 5 #define mem(a) memset(a,0,sizeof(a))
 6 #define inf 1e9
 7 #define ll long long
 8 #define succ(x) (1<<x)
 9 #define NM 16
10 #define nm 100+5
11 using namespace std;
12 int read(){
13     int x=0,f=1;char ch=getchar();
14     while(!isdigit(ch)){if(ch==‘-‘)f=-1;ch=getchar();}
15     while(isdigit(ch))x=x*10+ch-‘0‘,ch=getchar();
16     return x*f;
17 }
18 int n,m,a[NM],_t,d[succ(NM)];
19 double f[nm][succ(NM)];
20 int main(){
21     freopen("data.in","r",stdin);
22     n=read();m=read();
23     inc(i,1,m){
24         a[i]=read();
25         while(_t=read())d[i]+=succ(_t-1);
26     }
27     _t=succ(m)-1;
28     dec(i,n,1)
29     inc(j,0,_t){
30         inc(k,1,m)
31         if((d[k]&j)==d[k])f[i][j]+=max(f[i+1][j|succ(k-1)]+a[k],f[i+1][j]);
32         else f[i][j]+=f[i+1][j];
33         f[i][j]/=m;
34     }
35 //    inc(i,1,n){inc(j,0,_t)printf("%.1lf ",f[i][j]);printf("\n");}
36     printf("%.6lf",f[1][0]);
37     return 0;
38 }