31 lines
655 B
C++
31 lines
655 B
C++
#include <iostream>
|
|
#include <cstdio>
|
|
#include <cstring>
|
|
#include <algorithm>
|
|
using namespace std;
|
|
int n;
|
|
double f[1<<20], p[25];
|
|
int main()
|
|
{
|
|
while(scanf("%d", &n)!=EOF)
|
|
{
|
|
for(int i=0; i<n; i++)
|
|
scanf("%lf", &p[i]);
|
|
int all=(1<<n)-1;
|
|
f[all]=0;
|
|
for(int s=all-1; s>=0; s--)
|
|
{
|
|
double temp=0;
|
|
f[s]=1;
|
|
for(int i=0; i<n; i++)
|
|
{
|
|
if(s&(1<<i)) continue;
|
|
f[s]+=f[s|(1<<i)]*p[i];
|
|
temp+=p[i];
|
|
}
|
|
f[s]/=temp;
|
|
}
|
|
printf("%lf\n", f[0]);
|
|
}
|
|
}
|