fork download
copy 
  1. #include <iostream>
  2. #include <iomanip>
  3. #include <vector>
  4.  
  5. using namespace std;
  6.  
  7. int main() {
  8.     int N, M;
  9.     cin >> N >> M;
  10.  
  11.     // Read the favorite burgers of all people
  12.     vector<int> fav(N);
  13.     for (int i = 0; i < N; ++i) {
  14.         cin >> fav[i];
  15.     }
  16.  
  17.     int joshFav = fav[N-1];  // Josh's favorite burger (the last person's favorite)
  18.  
  19.     // Count how many people before Josh have the same favorite burger as Josh
  20.     int countJoshFavBefore = 0;
  21.     for (int i = 0; i < N - 1; ++i) {
  22.         if (fav[i] == joshFav) {
  23.             countJoshFavBefore++;
  24.         }
  25.     }
  26.  
  27.     // Initial probability that Josh's burger survives the coach's pick
  28.     double probability = 1.0;
  29.     probability *= (double)(M - 1) / M; // Chance that the coach doesn't pick Josh's burger
  30.  
  31.     // There are M-1 burgers left after the coach picks
  32.     int remainingBurgers = M - 1;
  33.  
  34.     // For every person who shares Josh's favorite burger, update the probability
  35.     for (int i = 0; i < N - 1; ++i) {
  36.         if (fav[i] == joshFav) {
  37.             probability *= (double)(remainingBurgers - 1) / remainingBurgers;
  38.             remainingBurgers--;
  39.         } else {
  40.             // If they don't care about Josh's burger, just reduce the number of burgers left
  41.             remainingBurgers--;
  42.         }
  43.     }
  44.  
  45.     // Output the final probability with six decimal precision
  46.     cout << fixed << setprecision(6) << probability << endl;
  47.  
  48.     return 0;
  49. }
  50.  
Success #stdin #stdout 0.01s 5280KB
comments (?)
stdin
copy 
3
1 2 3
stdout
copy 
0.000000
https://ideone.com/4W6HiB
language:
C++14 (clang 8.0)
created:
4 days ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!