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Meta·Machine Learning Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Went through a coding screen for an MLE role at Meta. One algorithm question, pretty focused on string manipulation. Nothing too wild but the two-pointer trick is easy to miss under pressure.

Questions Asked (1)

Q1

Given a string, return true if it can become a palindrome by removing at most one character.

Algorithms & Data Structures
Author's notes

My first instinct was brute force, try removing each character and check.

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AI HintsAI Generated

Suggested Approach

Use a two-pointer technique to check if the string is a palindrome, and when a mismatch occurs, try skipping either the left or right character and check if the remaining substring is a palindrome. This ensures O(n) time and O(1) space, which is optimal for this problem.

Pro tip: After coding, discuss edge cases like empty strings, single characters, and strings that are already palindromes, and mention that the solution handles them naturally. Also, briefly analyze time and space complexity to show thoroughness.

1. Clarify the problem

Confirm that 'removing at most one character' means we can remove zero or one character, and that the string consists of lowercase English letters (or clarify constraints).

2. Outline the two-pointer approach

Initialize left and right pointers at the start and end of the string. Move them inward while characters match.

3. Handle mismatch

When a mismatch occurs, check if the substring skipping the left character or skipping the right character is a palindrome. If either is, return true.

4. Implement helper function

Write a helper function that checks if a substring is a palindrome using two pointers, to avoid code duplication.

5. Analyze complexity and test

State that time complexity is O(n) and space is O(1). Walk through a few test cases, including edge cases.

Key Points to Mention

  • Two-pointer technique for palindrome checking
  • Greedy choice: try skipping either left or right character on mismatch
  • Helper function to check palindrome on a substring
  • Time complexity O(n) and space complexity O(1)
  • Edge cases: empty string, single character, already palindrome
  • At most one removal means zero removals are also allowed

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.