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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. #define print(a)         for(auto x : a) cout << x << " "; cout << endl
  6.  
  7.  
  8. const int M = 1000000007;
  9. const int N = 3e5+9;
  10. const int INF = 2e9+1;
  11. const int LINF = 2000000000000000001;
  12.  
  13. inline int power(int a, int b, int mod=M) {
  14.     int x = 1;
  15.     a %= mod;
  16.     while (b) {
  17.         if (b & 1) x = (x * a) % mod; 
  18.         a = (a * a) % mod;
  19.         b >>= 1;
  20.     }
  21.     return x;
  22. }
  23.  
  24.  
  25. //_ ***************************** START Below *******************************
  26.  
  27.  
  28.  
  29.  
  30. vector<int> a;
  31.  
  32.  
  33.  
  34.  
  35. int kSumPairs(vector<int>& a, int n, int k){
  36.  
  37. 	int ans = 0;
  38. 	int s = 0, e = n-1;
  39.  
  40. 	while(s<e){
  41. 		if(a[s] + a[e] > k){
  42. 			e--;
  43. 		}
  44. 		else if(a[s] + a[e] < k){
  45. 			s++;
  46. 		}
  47. 		else{
  48. 			ans++;
  49. 			s++;
  50. 			e--;
  51. 		}
  52. 	}
  53. 	return ans;
  54. }
  55.  
  56.  
  57. int consistency(int n){
  58. 	if(n<=1) return 0;
  59.  
  60. 	sort(begin(a), end(a));
  61.  
  62. 	int ans = 0;
  63.  
  64. 	for(int i=0; i<n; i++){
  65. 		for(int j=i+1; j<n; j++){
  66. 			ans = max(ans, kSumPairs(a, n, a[i]+a[j]));
  67. 		}
  68. 	}
  69.  
  70.  
  71. 	return ans;
  72. }
  73.  
  74.  
  75.  
  76.  
  77.  
  78.  
  79.  
  80.  
  81.  
  82.  
  83.  
  84.  
  85.  
  86.  
  87.  
  88.  
  89.  
  90.  
  91. int helper(vector<int>& a, int n, int k){
  92. 	int ans = 0;
  93. 	int s = 0, e = n-1;
  94. 	while(s<e){
  95. 		if(a[s] + a[e] > k){
  96. 			e--;
  97. 		}
  98. 		else if(a[s] + a[e] < k){
  99. 			s++;
  100. 		}
  101. 		else{
  102. 			ans++;
  103. 			e--;
  104. 			s++;
  105. 		}
  106. 	}
  107. 	return ans;
  108. }
  109.  
  110. int practice(int n){
  111.  
  112. 	sort(begin(a), end(a));
  113.  
  114. 	int ans = 0;
  115.  
  116. 	for(int i=0; i<=n-2; i++){
  117. 		for(int j=i+1; j<=n-1; j++){
  118. 			int k = a[i]+a[j];
  119.  
  120. 			ans = max(ans, helper(a, n, k));
  121.  
  122. 		}
  123. 	}
  124.  
  125.  
  126.     return ans;
  127. }
  128.  
  129.  
  130.  
  131.  
  132.  
  133. void solve() {
  134.  
  135.     int n;
  136.     cin>> n;
  137.  
  138.     a.resize(n);
  139.     for(int i=0; i<n; i++) cin >> a[i];
  140.  
  141.     cout << consistency(n) << endl;
  142.  
  143.     cout << practice(n) << endl;
  144.  
  145.  
  146. }
  147.  
  148.  
  149.  
  150.  
  151.  
  152. int32_t main() {
  153.     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  154.  
  155.     int t = 1;
  156.     // cin >> t;
  157.     while (t--) {
  158.         solve();
  159.     }
  160.  
  161.     return 0;
  162. }
Success #stdin #stdout 0.01s 5304KB
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https://ideone.com/uy4wvS
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

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