# 1299. Replace Elements with Greatest Element on Right Side

<https://leetcode.com/problems/replace-elements-with-greatest-element-on-right-side>

## Description

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 <= 104`
* `1 <= arr[i] <= 105`

## ac

```java
```