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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5. 	int n ;
  6. 	cin>>n;
  7. 	int target;
  8. 	cin>>target;
  9. 	int arr[n];
  10. 	for(int i = 0; i< n ; i++){
  11. 		cin>>arr[i];
  12. 	}
  13. 	int count = 0;
  14. 	unordered_map<int,int> mpp;
  15. 	for(int j = 0; j< n ; j++){
  16. 		int r = target - arr[j];
  17. 		if(mpp.count(r)){
  18. 			count += mpp[r];
  19. 		}
  20. 		mpp[arr[j]] = mpp[arr[j]] + 1;
  21. 	}
  22. 	cout << count;
  23.  
  24.     return 0;
  25. }
  26.  
Success #stdin #stdout 0.01s 5308KB
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stdin
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2 5 3 6 1
stdout
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https://ideone.com/kW6cQ6
language:
C++ (gcc 8.3)
created:
17 hours ago
visibility:
public

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