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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5.  
  6.     int n;int target;
  7.     cin>>n;cin>>target; 
  8.     vector <int> ar;
  9.     for(int i=0;i<=n-1;i++){
  10.     	int y;cin>>y; 
  11.     	ar.push_back(y); 
  12.     }
  13.  
  14. int count =0;
  15. unordered_map<int,int>mpp;
  16.  
  17. for(int j=0;j<n;j++){
  18. 	int rem = target-ar[j];
  19.  
  20. 	if(mpp.find(rem)!=mpp.end())
  21. 	count+=mpp[rem];
  22.  
  23. 	mpp[ar[j]]++;
  24. }
  25. cout<<count;
  26.  
  27. 	// your code goes here
  28. 	return 0;
  29. }
Success #stdin #stdout 0s 5320KB
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stdin
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6 5 
2 2 3 3 5 5
stdout
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4
https://ideone.com/y4OI4P
language:
C++ (gcc 8.3)
created:
19 hours ago
visibility:
public

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