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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. typedef long long ll;
  4. typedef vector<bool> vb;
  5. typedef vector<vb> vvb;
  6. typedef vector<int> vi;
  7. typedef vector<vi> vvi;
  8. typedef vector<ll> vl;
  9. typedef vector<vl> vvl;
  10. typedef vector<char> vc;
  11. typedef vector<vc> vvc ;
  12. typedef vector<string> vs;
  13. typedef vector<pair<ll, ll> > vp;
  14. typedef pair<ll, ll> pl;
  15.  
  16. #define endl "\n"
  17. #define pb push_back
  18. #define F first
  19. #define S second
  20. #define all(v) v.begin(), v.end()
  21. #define rall(v) v.rbegin(), v.rend()
  22. #define sz(a) int(a.size())
  23. const ll mod = 1e9+7;
  24.  
  25. ll n;
  26. long double dp[3001][3001];
  27. vector<long double> v;
  28.  
  29. long double f(ll x, ll o){	
  30. 	if(x>=n) {
  31. 		if(o>=(n+1)/2){
  32. 			return 1;
  33.  
  34. 		} else {
  35. 			return 0;
  36. 		}
  37. 	}
  38.  
  39. 	if(dp[x][o]!=-1)
  40. 		return dp[x][o];
  41.  
  42. 	dp[x][o]=v[x] * f(x+1, o+1) + (1-v[x]) * f(x+1, o);
  43.  
  44. 	return dp[x][o];
  45. }
  46.  
  47. void solve(){
  48. 	long double aux;
  49. 	cin >> n;
  50. 	for(ll i=0; i<n; i++){
  51. 		cin >> aux;
  52. 		v.pb(aux);
  53. 	}
  54.  
  55. 	for(ll i=0; i<n; i++){
  56. 		for(ll j=0; j<n; j++){
  57. 			dp[i][j]=-1;
  58. 		}
  59. 	}
  60.  
  61. 	std::cout << std::fixed << std::setprecision(10);
  62. 	cout << f(0, 0) << endl;
  63.  
  64. }
  65.  
  66. int main(){
  67.     ios::sync_with_stdio(false);
  68.     cin.tie(nullptr);
  69.  
  70.     int tt=1; 
  71.  
  72.     // cin >> tt;
  73.  
  74.     while(tt--){
  75.         solve();
  76.     }
  77. }
Success #stdin #stdout 0.01s 5316KB
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1.0000000000
https://ideone.com/4QN3MG
language:
C++14 (gcc 8.3)
created:
15 hours ago
visibility:
public

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