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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5. 	int k;cin>>k;
  6. int n; cin>>n;
  7. int f=0;
  8. unordered_map<int,int> mp;
  9. for(int i=0;i<n;i++){
  10. int t; cin>>t;
  11.  
  12.    f+=(mp[-t-k]);
  13. if(k!=0) f+=(mp[k-t]);
  14.  
  15.  
  16. mp[t]++;
  17.  
  18. }
  19. cout<<f;
  20. }
  21.  
Success #stdin #stdout 0s 5312KB
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stdin
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2
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stdout
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https://ideone.com/W28K2h
5
language:
C++14 (gcc 8.3)
created:
11 hours ago
visibility:
public

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