CODE EXAMPLE FOR CSHARP

replace elements with greatest element on right side

public class Solution 
{
    public int[] ReplaceElements(int[] arr)
    {
        int rightMax=-1;
        for(int i=arr.Length-1;i>=0;i--)
        {
           	int newMax=Math.Max(rightMax,arr[i]);
            arr[i]=rightMax;
            rightMax=newMax;
        }
        return arr;
    }
}