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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. //* Hashing Pairing
  35.  
  36. int kSumPairs(vector<int>& a, int n, int k){
  37.  
  38. 	int ans = 0;
  39.  
  40. 	unordered_map<int,int> mp;
  41. 	for(int i=0; i<n; i++){
  42. 		if(mp.count(k-a[i])){
  43. 			ans++;
  44. 			mp[k-a[i]]--;
  45. 		    if(mp[k-a[i]] == 0)  	mp.erase(k-a[i]);
  46. 		}
  47. 		else mp[a[i]]++;
  48. 	}
  49.  
  50. 	return ans;
  51. }
  52.  
  53. int consistency(int n){
  54. 	if(n<=1) return 0;
  55.  
  56. 	int ans = 0;
  57.  
  58. 	for(int i=0; i<n; i++){
  59. 		for(int j=i+1; j<n; j++){
  60. 			ans = max(ans, kSumPairs(a, n, a[i]+a[j]));
  61. 		}
  62. 	}
  63.  
  64.  
  65. 	return ans;
  66. }
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  89.  
  90.  
  91. int practice(int n){
  92.  
  93.  
  94.     return 0;
  95. }
  96.  
  97.  
  98.  
  99.  
  100.  
  101. void solve() {
  102.  
  103.     int n;
  104.     cin>> n;
  105.  
  106.     a.resize(n);
  107.     for(int i=0; i<n; i++) cin >> a[i];
  108.  
  109.     cout << consistency(n)  << endl;
  110.  
  111.  
  112. }
  113.  
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  115.  
  116.  
  117.  
  118. int32_t main() {
  119.     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  120.  
  121.     int t = 1;
  122.     // cin >> t;
  123.     while (t--) {
  124.         solve();
  125.     }
  126.  
  127.     return 0;
  128. }
Success #stdin #stdout 0s 5320KB
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https://ideone.com/aUz92V
language:
C++14 (gcc 8.3)
created:
14 hours ago
visibility:
public

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