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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5. 	int n,target;
  6. 	cin>>n>>target;
  7.  
  8. 	vector<int> numbers(n);
  9.  
  10. 	for(auto& number: numbers){
  11. 		cin>>number;
  12. 	}
  13.  
  14. 	int answer = 0;
  15.  
  16. 	unordered_map<int,int> freq;
  17.  
  18. 	for(int i=0; i<n; i++){
  19.  
  20.  
  21. 		int reqNum = target + numbers[i];
  22.  
  23. 		if(freq.find(reqNum) != freq.end())answer+= freq[reqNum];
  24.  
  25. 		freq[numbers[i]]++;
  26. 	}
  27.  
  28. 	cout<<answer;
  29.  
  30. 	return 0;
  31. }
Success #stdin #stdout 0s 5304KB
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stdin
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6 2
5 5 3 3 2 2
stdout
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4
https://ideone.com/PQ75ph
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

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