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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. #define ll long long
  4. #define nmax 3001
  5. double p[nmax] , p1[nmax];
  6. ll n;
  7. bool visited[nmax][nmax];
  8. double dp[nmax][3005];
  9. double tinh(int index , int ch){
  10.     if (index == n + 1){
  11.         int ct =  n- ch;
  12.         return(ch > ct and ch <= n)? 1.0 : 0.0;
  13.     }
  14.     if (visited[index][ch]) return dp[index][ch];
  15.     visited[index][ch] = true;
  16.     double ans = 0;
  17.     ans+= p[index] * tinh(index + 1 , ch + 1);
  18.     ans+= p1[index] *tinh(index + 1 , ch);
  19.     return dp[index][ch] = ans;
  20. }
  21. void solve(){
  22.     memset(dp , -1 , sizeof(dp));
  23.     cin >> n;
  24.     for (int i = 1 ; i <= n ; i++){
  25.         cin >> p[i];
  26.         p1[i] = 1.0 - p[i];
  27.     }
  28.     cout << fixed << setprecision(10) << tinh(1 , 0);
  29. }
  30. int main(){
  31.     solve();
  32. }
  33.  
Success #stdin #stdout 0.02s 74464KB
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Standard input is empty
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0.0000000000
https://ideone.com/E8jcMh
language:
C++ (gcc 8.3)
created:
7 days ago
visibility:
public

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