zoj 3696 Alien's Organ

/* ***********************************************
Author        :xryz
Email         :523689985@qq.com
Created Time  :4-26 12:05:01
File Name     :zoj3696.cpp
************************************************ */

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <time.h>
using namespace std;

int main()
{
    int T,i,n;
    double ans,q;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d %lf",&n,&q);
        double t=exp(-q);
        ans=t;
        for(i=1;i<=n;i++)
        {
            t*=q/i;
            ans+=t;
        }

        printf("%.3f\n",ans);
    }
    return 0;
}

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