Replace Elements with Greatest Element on Right Side in C++

Suppose we have an array A. We have to replace every element by the greatest element on the right side of this element. And replace the last one by -1. So if A = [5, 17, 40, 6, 3, 8, 2], then it will be [40,40,8,8,8,2,-1]

To solve this, we will follow these steps −

• We will read the array element from right to left.
• take e := -1
• for i := n – 1 to 0
  • temp := e
  • e := max between e and array[i]
  • array[i] := temp
• return array

Example

Let us see the following implementation to get better understanding −

 Live Demo

#include <bits/stdc++.h>
using namespace std;
void print_vector(vector<int> v){
   cout << "[";
      for(int i = 0; i<v.size(); i++){
         cout << v[i] << ", ";
      }
      cout << "]"<<endl;
}
class Solution {
   public:
      vector<int> replaceElements(vector<int>& arr) {
         int rep = -1;
         int n = arr.size();
         for(int i = n - 1; i >= 0; i--){
            int temp = rep;
            rep = max(rep, arr[i]);
            arr[i] = temp;
         }
         return arr;
      }
};
main(){
   Solution ob;
   vector<int> c = {5,17,40,6,3,8,2};
   print_vector(ob.replaceElements(c)) ;
}

Input

[5,17,40,6,3,8,2]

Output

[40,40,8,8,8,2,-1]