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  1. #include<bits/stdc++.h>
  2. #include <iostream>
  3. using namespace std;
  4.  
  5. int countPair(vector<int> arr,int k){
  6.     unordered_map<int,int> freq;
  7.     int count=0;
  8.     for(int i=0;i<arr.size();i++){
  9.         int complement=k+arr[i];
  10.         if(freq.find(complement) != freq.end()){
  11.             count = count+freq[complement];
  12.         }
  13.  
  14.         freq[arr[i]]++;
  15.  
  16.     }
  17.     return count;
  18.  
  19. }
  20.  
  21. int main(){
  22.     vector<int> arr={1, 5, 3, 4, 2};
  23.     int k=2;
  24.     cout<<"No. of Pairs: "<<countPair(arr,k);
  25. }
Success #stdin #stdout 0.01s 5288KB
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stdin
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Standard input is empty
stdout
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No. of Pairs: 2
https://ideone.com/mocX1o
language:
C++14 (gcc 8.3)
created:
6 days ago
visibility:
public

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