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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. int main()
  4. {
  5.     int n;cin>>n;
  6.     int k;cin>>k;
  7.     vector<int> arr(n);
  8.     unordered_map<int,int> mp;
  9.     int count=0;
  10.     for(int j=0;j<n;j++)
  11.     {
  12.         cin>>arr[j];
  13.         int x=k-arr[j];
  14.         count+=mp[x];
  15.         mp[arr[j]]++;
  16.     }
  17.     cout<<count;
  18.  
  19.  
  20.  
  21.  
  22. }
  23.  
  24.  
  25.  
  26.  
Success #stdin #stdout 0.01s 5280KB
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stdout
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Standard output is empty
https://ideone.com/9AR8e6
language:
C++ (gcc 8.3)
created:
9 hours ago
visibility:
public

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