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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main(){
  5.     int n,k,cnt=0;
  6.     cin>>n>>k;
  7.     vector<int>v(n);
  8.     unordered_map<int,int>mp;
  9.     for(auto &it:v){
  10.         cin>>it;
  11.         mp[it]++;
  12.     }
  13.     for(auto &it:mp){
  14.         if(mp.find(it.first-k)!=mp.end()){
  15.             if(k==0) cnt+=(it.second*(it.second-1))/2;
  16.             else cnt+=it.second*mp[it.first-k];
  17.  
  18.         }
  19.     }
  20.     cout<<cnt<<"\n";
  21.     return 0;
  22. }
Success #stdin #stdout 0s 5300KB
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https://ideone.com/Jd6hv1
language:
C++14 (gcc 8.3)
created:
6 days ago
visibility:
public

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