24 January Convert an array to reduced form

class Solution{
public: 
 // Converts arr[0..n-1] to reduced form.
 void convert(int arr[], int n) {
     //push the value and its index as pair into a vector
     vector<pair<int,int>> v;
     for(int i=0; i<n; i++){
         v.push_back({arr[i], i});
     }
     //sort them according to the value
     sort(v.begin(), v.end());
     
     int k=0;
     //replace each position with the reduced value
     for(auto it : v){
         arr[it.second] = k;
         k++;
     }
 }

};