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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5. 	int arr[]= {10, 5, 1, 3, 1};
  6. 	int n=sizeof(arr)/sizeof(arr[0]);
  7. 	int diff=2;
  8. 	int count=0;
  9. 	unordered_map<int, int> mp;
  10. 	for(int j=0;j<n;j++){
  11. 		if(mp.find(diff-arr[j])!=mp.end())
  12. 			count=count+mp[diff-arr[j]];
  13. 		if(mp.find(-diff-arr[j])!=mp.end())
  14. 			count=count+mp[-diff-arr[j]];
  15. 		mp[arr[j]]++;
  16. 	}
  17. 	cout<<count;
  18. 	return 0;
  19. }
  20.  
Success #stdin #stdout 0.01s 5292KB
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https://ideone.com/nhUPsC
language:
C++ (gcc 8.3)
created:
1 hour ago
visibility:
public

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