Walmart Labs·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

May 2026

Summary

Walmart Labs SWE interview with a string manipulation question that looks deceptively simple until you start thinking about edge cases.

Questions Asked (1)

Given a palindrome string like 'abcxyba', insert spaces so that the mirrored characters are visually separated from the non-palindromic center, resulting in something like 'a b cxy b a'.

Algorithms & Data Structures

Author's notes

Took me a minute to even parse what the output was supposed to look like.

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AI HintsAI Generated

Suggested Approach

First, clarify the problem by restating it and confirming edge cases. Then, outline a two-pointer approach to identify the non-palindromic center, and finally, describe how to insert spaces around that center to separate mirrored characters.

Pro tip: Mention that the center can be found by comparing characters from both ends until they differ or meet, and emphasize that the solution should handle both odd and even length palindromes.

1. Clarify the problem

Restate the problem in your own words and ask clarifying questions about input format, output format, and edge cases (e.g., empty string, single character, even-length palindromes).

2. Identify the non-palindromic center

Use two pointers starting at the beginning and end of the string, moving inward while characters match. The center is the substring between the pointers when they stop matching or cross.

3. Insert spaces around the center

Construct the output by placing a space between each mirrored character and the center substring. For example, for 'abcxyba', the center is 'cxy', so the result is 'a b cxy b a'.

4. Handle edge cases

Consider cases where the entire string is a palindrome (no non-palindromic center) or where the center is empty (even-length palindrome). Adjust the spacing logic accordingly.

5. Analyze complexity

State that the time complexity is O(n) with a single pass to find the center and O(n) to build the output, and space complexity is O(n) for the output string.

Key Points to Mention

Two-pointer technique to find the center
Handling odd and even length palindromes
Edge cases: empty string, single character, full palindrome
Time and space complexity analysis
String manipulation and output construction
Clarifying the definition of 'mirrored characters' and 'non-palindromic center'

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