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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.         hmap[arr[i]]++;
  14.  
  15.     }
  16. return cnt;    
  17. }
  18. int main(){
  19.     vector<int> arr={1,2,3,4,5,5};
  20.     int k=6;
  21.  
  22.     cout<<count(arr,k);
  23.  
  24. }
Success #stdin #stdout 0s 5312KB
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https://ideone.com/pyqYMq
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

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