Replace Elements with Greatest Element on Right Side Python/Java solution

The typical Python or Java solution iterates from the last index to the first while maintaining a maxRight variable. At each step, the element is replaced with maxRight and the variable is updated with the maximum of the current element and maxRight. This results in O(n) time and constant space.

How to solve Replace Elements with Greatest Element on Right Side in O(n)?

Traverse the array from right to left while keeping a variable called maxRight. Replace the current element with maxRight, then update maxRight using the original value of that element. This maintains the maximum of all elements to the right without rescanning the array.

What is the best approach for Replace Elements with Greatest Element on Right Side?

The best approach is reverse iteration from the end of the array while maintaining the maximum value seen so far. For each index, replace the current element with the stored maximum and then update the maximum if the current element is larger. This processes each element once, resulting in O(n) time and O(1) extra space.

Is Replace Elements with Greatest Element on Right Side asked at Google/Amazon/Meta?

Array transformation and suffix maximum problems appear frequently in interviews at companies like Amazon and Google. While this exact question may not always appear verbatim, the reverse traversal and running maximum pattern is commonly tested in coding interviews.

What data structure is used in Replace Elements with Greatest Element on Right Side?

The problem primarily uses a simple array with a running variable to track the suffix maximum. No additional data structures like stacks or hash maps are required in the optimal solution, which keeps the space complexity at O(1).

What is the time complexity of Replace Elements with Greatest Element on Right Side?

The optimal solution runs in O(n) time because the array is traversed exactly once from right to left. A running variable stores the maximum value seen so far. The brute force approach takes O(n^2) time since it scans the remaining elements for every index.

Description Hints 2 Solution Video 8:58

1299. Replace Elements with Greatest Element on Right Side

Q: Is Replace Elements with Greatest Element on Right Side easy or hard?

The problem is categorized as Easy because it mainly tests array traversal and recognizing a suffix maximum pattern. Once you realize that scanning from the right avoids repeated work, the implementation becomes a short linear pass.

Easy72.6% acceptance4 companies

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

Asked at 4 companies

Zoho Amazon

Google Meta

Topics

Array

Hints open one at a time

Hint 1

Loop through the array starting from the end.

Hint 2

Keep the maximum value seen so far.

8:58

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