FZU 2132 && FOJ11月赛A题 概率

//不大会搞这类题，借个代码

#include<stdio.h>#include<algorithm>#include<iostream>#include<math.h>using namespace std;double cal(int n,int k,double p){double sum=pow(p,k)*pow(1-p,n-k);for(int i=1;i<=k;i++)sum=sum*(n+1-i)/i;return sum;}int main(){    int a,n,T;    double x;    scanf("%d",&T);    while(T--)    {           scanf("%d",&n);           scanf("%d%lf",&a,&x);           double sum=0.0,k=1;           for(int i=a;i<=n;i++) sum+=cal(n,i,x);           printf("%.4lf\n",sum);    }     return 0;}