43 lines
990 B
C++
43 lines
990 B
C++
#include <iostream>
|
|
#include <cstdio>
|
|
#include <cstring>
|
|
#include <algorithm>
|
|
using namespace std;
|
|
double dp[1550];
|
|
double power[1550];
|
|
double ans[1550];
|
|
double pre[1550];
|
|
int main(){
|
|
int T,n;
|
|
double p,q;
|
|
scanf("%d",&T);
|
|
while(T--){
|
|
scanf("%d%lf%lf",&n,&p,&q);
|
|
power[0]=1;
|
|
double pro0=q/p;
|
|
double pro1=(p-q)/p;
|
|
for(int i=1;i<=n+1;i++){
|
|
power[i]=power[i-1]*pro0;
|
|
}
|
|
ans[0]=0;
|
|
n++;
|
|
for(int i=1;i<=n;i++){
|
|
dp[0]=pre[0]=1;
|
|
for(int j=1;j<=n;j++){
|
|
double now=pre[j-1];
|
|
if(j-1-i>=0) now-=pre[j-1-i]*power[i];
|
|
dp[j]=now*pro1;
|
|
pre[j]=pre[j-1]*pro0+dp[j];
|
|
}
|
|
ans[i]=dp[n];
|
|
}
|
|
double e=0;
|
|
for(int i=n;i>=1;i--){
|
|
e+=(ans[i]-ans[i-1])*i;
|
|
}
|
|
e/=pro1;
|
|
printf("%.3lf\n",e);
|
|
}
|
|
return 0;
|
|
}
|