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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define int              long long int
  4. #define double           long double
  5. inline int power(int a, int b) {
  6.     int x = 1;
  7.     while (b) {
  8.         if (b & 1) x *= a;
  9.         a *= a;
  10.         b >>= 1;
  11.     }
  12.     return x;
  13. }
  14.  
  15.  
  16. const int M = 1000000007;
  17. const int N = 3e5+9;
  18. const int INF = 2e9+1;
  19. const int LINF = 2000000000000000001;
  20.  
  21. //_ ***************************** START Below *******************************
  22.  
  23.  
  24.  
  25. vector<int> a;
  26.  
  27. //* O(n^2)
  28. void consistency1(int n, int k1, int k2) {
  29.  
  30. 	int ans = 0;
  31. 	for(int j=1; j<n-2; j++){
  32. 		int i=0;
  33. 		while(i<j){
  34. 			if(a[i] + a[j] >= k1) break;
  35. 			i++;
  36. 		}
  37. 		int leftCt = j-i;
  38.  
  39. 		int  s= j+1, e = n-1;
  40. 		int rightCt = 0;
  41. 		while(s<e){
  42. 			int sum = a[s] + a[e];
  43. 			if(sum > k2){
  44. 				rightCt += (e-s);
  45. 				e--;
  46. 			}
  47. 			else{
  48. 				s++;
  49. 			}
  50. 		}
  51. 		ans += leftCt * rightCt;
  52. 	}
  53.  
  54. 	cout << ans << endl;
  55. }
  56.  
  57.  
  58.  
  59.  
  60. //* O(n^2)
  61. void consistency2(int n, int k1, int k2) {
  62.  
  63. 	int ans = 0;
  64.  
  65. 	vector<int> p(n);
  66. 	for(int i=0; i<n-1; i++){
  67. 		int target = k2 - a[i];
  68. 		int j = lower_bound(a.begin() + i + 1, a.end(), target) - a.begin();
  69. 		p[i] = n-j;
  70. 	}
  71. 	vector<int> rightSufix(n);
  72. 	for(int i=n-2; i>=0; i--){
  73. 		rightSufix[i] = rightSufix[i+1] + p[i];
  74. 	}
  75.  
  76.  
  77. 	for(int j=1; j<n-2; j++){
  78. 		int target = k1 - a[j];
  79. 		int i = lower_bound(a.begin(), a.begin()+j, target) - a.begin();
  80. 		int leftCt = j-i;
  81.  
  82. 		int rightCt = rightSufix[j+1];
  83.  
  84. 		ans += leftCt * rightCt;
  85.  
  86. 	}
  87.  
  88.  
  89. 	cout << ans << endl;
  90.  
  91. }
  92.  
  93.  
  94. void solve() {
  95.  
  96. 	int n, k1, k2;
  97. 	cin >> n >> k1 >> k2;
  98.  
  99. 	a.resize(n);
  100. 	for(int i=0; i<n; i++) cin >> a[i];
  101.  
  102.     consistency1(n, k1, k2);
  103.     consistency2(n, k1, k2);
  104.  
  105. }
  106.  
  107.  
  108.  
  109.  
  110.  
  111. int32_t main() {
  112.     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  113.  
  114.     int t = 1;
  115.     // cin >> t;
  116.     while (t--) {
  117.         solve();
  118.     }
  119.  
  120.     return 0;
  121. }
Success #stdin #stdout 0.01s 5292KB
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https://ideone.com/1Nu58c
language:
C++14 (gcc 8.3)
created:
3 days ago
visibility:
public

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