BZOJ4008/HNOI2015 亚瑟王(期望dp)

/**************************************************************
Problem: 4008
User: DtenSherlock
Language: C++
Result: Accepted
Time:2928 ms
Memory:1528 kb
****************************************************************/
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cmath>
#include<cstring>
#include<string>
using namespace std;
const int imax=229;
const int kmax=132+9;
int T,n,m;
double p[imax],d[imax];
double f[imax][kmax];

int main()
{
scanf("%d",&T);
while(T--)
{
scanf("%d%d",&n,&m);
for(int i=1;i<=n;i++) scanf("%lf%lf",&p[i],&d[i]);
memset(f,0,sizeof(f));

f[0][m]=1;
for(int i=1;i<=n;i++)
for(int j=1;j<=m;j++)
f[i][j]=f[i-1][j]*pow(1-p[i-1],j)+f[i-1][j+1]*(1.0-pow(1-p[i-1],j+1));
double ans=0;
for(int i=1;i<=n;i++)
for(int j=1;j<=m;j++)
ans+=f[i][j]*(1.0-pow(1-p[i],j))*d[i];

printf("%.10lf\n",ans);
}
return 0;
}