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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. class Coins1 {
  5. public:
  6.   double moreHead(vector<double>& probs, int n) {
  7.     vector<vector<double>> dp(n+1, vector<double>(n+1, 0.0));
  8.  
  9.     dp[0][0] = 1.0;
  10.  
  11.     for(int i = 1; i <= n; ++i) {
  12.       dp[i][0] = dp[i-1][0] * (1 - probs[i-1]);
  13.       for(int j = 1; j <= i; ++j) {
  14.         dp[i][j] =
  15.             dp[i-1][j]   * (1 - probs[i-1])
  16.           + dp[i-1][j-1] * probs[i-1];
  17.       }
  18.     }
  19.  
  20.     double ans = 0.0;
  21.     for(int j = n/2 + 1; j <= n; ++j) {
  22.       ans += dp[n][j];
  23.     }
  24.     return ans;
  25.   }
  26. };
  27.  
  28. int main() {
  29.   int n; 
  30.   cin >> n;
  31.   vector<double> probs(n);
  32.   for(int i = 0; i < n; ++i) cin >> probs[i];
  33.  
  34.   Coins1 obj;
  35.   cout << fixed << setprecision(10)
  36.        << obj.moreHead(probs, n) << endl;
  37.   return 0;
  38. }
  39.  
Success #stdin #stdout 0s 5316KB
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stdout
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0.3821815872
https://ideone.com/Cd1VIF
language:
C++ (gcc 8.3)
created:
5 hours ago
visibility:
public

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