FIND THE PAIR IN AN ARRAY FOR A GIVEN SUM USING HASH TECHNIQUE(OPTIMIZED)

Hii friends,here find the optimize version of the above problem.If u have any doubt let me know

#include<bits/stdc++.h>
using namespace std;
int main(){

  int n,i,j;
  cout << "Enter the size of array:\n";
  cin >> n;
  int arr[n];

  cout << "Enter the elements of array:\n";
  for(i=0;i<n;i++){
   cin >> arr[i];
  }

  int sum;
  cout << "Enter the value of sum:\n";
  cin>> sum;

  //Using hash technique
  map<int,int> hash;
  for(i=0;i<n;i++){
   hash[arr[i]]=1;
  }

  for(i=0;i<n;i++){
   if(hash.find(sum-arr[i])!=hash.end()){
    cout << arr[i] << " " << sum-arr[i] << endl;

    hash.erase(arr[i]);//to remove duplicates pair
   }
  }




 return 0;
}