wenbao与概率

 1 #include <iostream>
 2 #include <cmath>
 3 using namespace std;
 4 double x, sum;
 5 int n, m, t;
 6 double f(int x){
 7     double num = 1;
 8     while(x > 0){
 9         num *= (double)x;
10         x--;
11     }
12     return num;
13 }
14 double C(int i, int n){
15     return f(n)/f(i)/f(n-i);
16 }
17 int main(){
18     scanf("%d", &t);
19     while(t--){
20         sum = 0;
21         scanf("%d%d%lf", &n, &m, &x);
22         for(int i = m; i <= n; ++i){
23             sum = (sum + C(i, n)*pow(x, i)*pow(1-x, n-i));
24         }
25         printf("%.4lf\n", sum);
26     }
27     return 0;
28 }