hdu 4336 Card Collector

dp+状态压缩

 #include<cstdio>
 using namespace std;
 double p[];
 double dp[<<];
 int main()
 {
     int n;
     while(scanf("%d",&n)!=EOF)
     {
         for(int i=; i<n; i++)
             scanf("%lf",&p[i]);
         dp[(<<n)-]=;
         for(int i=(<<n)-; i>=; i--)
         {
             dp[i]=1.0;
             double sum=0.0;
             for(int j=; j<n; j++)
             {
                 if(i&(<<j)) continue;
                 sum+=p[j];
                 dp[i]+=dp[i|(<<j)]*p[j];
             }
             //printf("%lf %lf==\n",dp[i],sum);
             dp[i]=dp[i]/sum;
         }
         printf("%lf\n",dp[]);
     }
     return ;
 }