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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int count(vector<int>&arr , int k){
  5.     unordered_map<int,int>hmap;
  6.     int cnt=0; 
  7.     for(int i=0;i<arr.size();i++){
  8.  
  9.  
  10.         if(hmap.find(k+arr[i])!=hmap.end() ){
  11.             cnt+=hmap[k+arr[i]];
  12.         }
  13.         if(k!=0 && hmap.find(arr[i]-k)!=hmap.end()){
  14.             cnt+=hmap[arr[i]-k];
  15.         }
  16.         hmap[arr[i]]++;
  17.  
  18.     }
  19. return cnt;    
  20. }
  21. int main(){
  22.     vector<int> arr={1, 5, 3, 4, 2};
  23.     int k=2;
  24.  
  25.     cout<<count(arr,k);
  26.  
  27. }
Success #stdin #stdout 0s 5312KB
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stdin 
Standard input is empty
stdout 
3
https://ideone.com/a74wsv
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

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