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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5. 	int n; cin >> n;
  6. 	vector<int> arr(n);
  7. 	for(int i = 0; i < n; i++)
  8. 	cin >> arr[i];
  9.  
  10. 	int res = INT_MIN;
  11.  
  12. 	for(int i = 0; i < n; i++){
  13. 		for(int j = i+1; j < n; j++){
  14. 			int l = arr[i]+arr[j];
  15.  
  16. 			unordered_map<int,int> mp;
  17. 	        for(int k = 0; k < n; k++){
  18. 	            mp[arr[k]]++;
  19. 	        }
  20. 	        int ans = 0;
  21. 	        unordered_map<int,int> vis;
  22. 	        for(auto k : mp){
  23. 	            int val = k.first;
  24. 	            int freq = k.second;
  25. 	            int req = l-val;
  26. 	            if(vis.find(val) != vis.end() || vis.find(req) != vis.end())
  27. 	            continue;
  28. 	            if(mp.find(req) != mp.end()){
  29. 	                if(val == req)
  30. 	                ans += freq/2;
  31. 	                else{
  32. 	                    ans += min(freq, mp[req]);
  33. 	                }
  34. 	                vis[req]++;
  35. 	                vis[val]++;
  36. 	            }
  37. 	        }
  38. 	        res = max(res,ans);
  39. 		}
  40. 	}
  41. 	cout << res;
  42. 	return 0;
  43. }
Success #stdin #stdout 0s 5320KB
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https://ideone.com/fxr6x5
language:
C++14 (gcc 8.3)
created:
8 days ago
visibility:
public

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