'''
Given an array arr, replace every element in that array with the greatest element among the elements to its right, and replace the last element with -1.

After doing so, return the array.



Example 1:

Input: arr = [17,18,5,4,6,1]
Output: [18,6,6,6,1,-1]


Constraints:

1 <= arr.length <= 10^4
1 <= arr[i] <= 10^5
'''


class Solution:
    def replaceElements(self, arr: List[int]) -> List[int]:
        rightmax = -1
        for n in range(len(arr)-1, -1, -1):
            rightmax, arr[n] = max(rightmax, arr[n]), rightmax
        return arr