## Question

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]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.

**Example 2:**

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

**Constraints:**

`1 <= arr.length <= 10`

^{4}`1 <= arr[i] <= 10`

^{5}

## Python Solution

class Solution: def replaceElements(self, A, mx = -1): for i in range(len(A) - 1, -1, -1): A[i], mx = mx, max(mx, A[i]) return A