HNOI2015 亚瑟王

#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cmath>
#include<cstring>

using namespace std;

int dt,tj,i,n,m,j;
double ans;

struct card{
    double p,d;
}a[231];

double d[231],f[231][231],p[231][231];

int main()
{
    scanf("%d",&dt);
    for(tj=1;tj<=dt;tj++){
        scanf("%d%d",&n,&m);
        for(i=1;i<=n;i++)scanf("%lf%lf",&a[i].p,&a[i].d);
        memset(f,0,sizeof(f));
        memset(d,0,sizeof(d));
        f[m][0]=1;
        for(i=1;i<=n;i++)p[i][1]=1-a[i].p;
        for(i=2;i<=m;i++)
            for(j=1;j<=n;j++)p[j][i]=p[j][i-1]*(1-a[j].p);
        for(i=m;i>=1;i--){
            for(j=0;j<n;j++){
                f[i][j+1]+=f[i][j]*p[j+1][i];
                f[i-1][j+1]+=f[i][j]*(1-p[j+1][i]);
                d[j+1]+=f[i][j]*(1-p[j+1][i]);
            }
        }
        ans=0;
        for(i=1;i<=n;i++)ans+=a[i].d*d[i];
        printf("%.11lf\n",ans);
    }
}