Question

1299. Replace Elements with Greatest Element on Right Side

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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

Solutions

Solution 1

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

class Solution {
  public int[] replaceElements(int[] arr) {
    for (int i = arr.length - 1, max = -1; i >= 0; --i) {
      int t = arr[i];
      arr[i] = max;
      max = Math.max(max, t);
    }
    return arr;
  }
}