Replace Elements with Greatest Element on

lcpy gen -n 1299   # by problem number
lcpy gen -s replace_elements_with_greatest_element_on_right_side   # by problem name

Input: arr = [17,18,5,4,6,1]
Output: [18,6,6,6,1,-1]
Explanation:
- index 0 --> the greatest element to the right of index 0 is index 1 (18).
- index 1 --> the greatest element to the right of index 1 is index 4 (6).
- index 2 --> the greatest element to the right of index 2 is index 4 (6).
- index 3 --> the greatest element to the right of index 3 is index 4 (6).
- index 4 --> the greatest element to the right of index 4 is index 5 (1).
- index 5 --> there are no elements to the right of index 5, so we put -1.

Input: arr = [400]
Output: [-1]
Explanation: There are no elements to the right of index 0.

class Solution:
    def replace_elements(self, arr: list[int]) -> list[int]:
        result = [-1] * len(arr)
        best = -1
        for i in range(len(arr) - 1, -1, -1):
            result[i] = best
            best = max(best, arr[i])
        return result