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  1. #include <iostream>
  2. #include <cstdio>
  3. #include <algorithm>
  4. #include <vector>
  5. using namespace std;
  6. #define SZ(a) (int)(a).size()
  7. typedef long long ll;
  8.  
  9. #include <ext/pb_ds/assoc_container.hpp> // Common file
  10. #include <ext/pb_ds/tree_policy.hpp>     // Including tree_order_statistics_node_update
  11.  
  12. using namespace __gnu_pbds;
  13.  
  14. typedef tree<double, null_type, greater<double>, rb_tree_tag, tree_order_statistics_node_update> oset;
  15.  
  16. const auto eps = 1e-3;
  17. const auto mlpy = 10;
  18. int n, l, r;
  19. ll m;
  20. vector<double> a;
  21. int nr;
  22.  
  23. bool f(double mean) {
  24. 	auto k = 0ll;
  25. 	vector<double> b(n+1);
  26. 	b[0] = 0;
  27. 	for (auto i = 1; i <= n; i++) {
  28. 		b[i] = b[i-1]+a[i-1]-mean;
  29. 	}
  30. 	oset o;
  31. 	for (auto i = l; i <= n; i++) {
  32. 		auto s = b[i-l];
  33. 		while (!o.insert(s).second) {
  34. 			s = b[i-l]+(double)(rand()%nr)/nr*eps;
  35. 		}
  36. 		if (i >= r) {
  37. 			o.erase(o.lower_bound(b[i-r]));
  38. 		}
  39. 		k += o.order_of_key(b[i]+eps);
  40. 		if (k >= m) {
  41. 			return true;
  42. 		}
  43. 	}
  44. 	return false;
  45. }
  46.  
  47. double bsearch(double lo, double up) {
  48. 	auto mi = (lo+up)/2;
  49. 	if (up-lo < eps) {
  50. 		return mi;
  51. 	}
  52. 	if (f(mi)) {
  53. 		bsearch(lo, mi);
  54. 	}
  55. 	else {
  56. 		bsearch(mi, up);
  57. 	}
  58. }
  59.  
  60. int main() {
  61. 	cin.sync_with_stdio(false);
  62. 	cin >> n >> l >> r >> m;
  63. 	r++;
  64. 	nr = n*mlpy;
  65. 	a.resize(n);
  66. 	for (auto i = 0; i < n; i++) {
  67. 		cin >> a[i];
  68. 	}
  69. 	auto ans = bsearch(1.0, 1e6);
  70. 	printf("%f\n", ans);
  71. 	return 0;
  72. }
  73.  
Success #stdin #stdout 0s 16072KB
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https://ideone.com/eQtA3S
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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