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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.  
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  78.  
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  80.  
  81.  
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  88.  
  89.  
  90.  
  91.  
  92.  
  93. int practice(int n){
  94.  
  95.  
  96.     return 0;
  97. }
  98.  
  99.  
  100.  
  101.  
  102.  
  103. void solve() {
  104.  
  105.     int n;
  106.     cin>> n;
  107.  
  108.     a.resize(n);
  109.     for(int i=0; i<n; i++) cin >> a[i];
  110.  
  111.     cout << consistency(n) << endl;
  112.  
  113.  
  114. }
  115.  
  116.  
  117.  
  118.  
  119.  
  120. int32_t main() {
  121.     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  122.  
  123.     int t = 1;
  124.     // cin >> t;
  125.     while (t--) {
  126.         solve();
  127.     }
  128.  
  129.     return 0;
  130. }
Success #stdin #stdout 0s 5320KB
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https://ideone.com/UuYC7M
language:
C++14 (gcc 8.3)
created:
14 hours ago
visibility:
public

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