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LeetCode solutions

1231. Replace Elements with Greatest Element on Right Side

My accepted Python solution to LeetCode problem 1231, Replace Elements with Greatest Element on Right Side, running in 55ms.

  • Difficulty: Easy
  • Python
  • Runtime 55ms
  • Memory 18.6MB

Read the problem on LeetCode View on GitHub

The problem statement is LeetCode’s and stays on their site. What follows is my accepted solution.

Python

Accepted on LeetCode — runtime 55ms, memory 18.6MB, accepted 2025-12-29.

python
class Solution:
    def replaceElements(self, arr: List[int]) -> List[int]:
        # Iterate from right to left, tracking max seen so far
        # Time: O(n), Space: O(1) - modify in place
        max_right = -1
        for i in range(len(arr) - 1, -1, -1):
            new_val = max_right
            max_right = max(max_right, arr[i])
            arr[i] = new_val
        return arr

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