Google·Machine Learning Engineer·Technical Phone Screen·Senior

SeniorPrefer not to say

Jul 2026

Summary

Interviewed for an ML engineer role at Google and got a string manipulation problem that looked deceptively simple at first glance.

Questions Asked (1)

Given two strings of equal length, is it possible to cut each string in half and combine the halves to form a palindrome?

Algorithms & Data Structures

Author's notes

Spent the first few minutes just staring at the constraints.

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AI HintsAI Generated

Suggested Approach

Clarify that the operation is to cut each string into two halves and then combine one half from each string (in either order) to form a new string. Then, systematically check all possible combinations (at most 4) to see if any is a palindrome, and discuss the time complexity.

Pro tip: After presenting the brute-force check, mention that the problem can be solved in O(n) time by checking specific conditions on the halves, showing you can optimize beyond the obvious solution.

1. Clarify the operation

Confirm that cutting each string in half yields two halves per string, and that combining means concatenating one half from each string (order can vary).

2. Enumerate combinations

List all possible concatenations: A1+B1, A1+B2, A2+B1, A2+B2 (where A1, A2 are halves of first string, B1, B2 of second).

3. Check for palindrome

For each combination, check if it reads the same forwards and backwards. If any is a palindrome, return true; else false.

4. Analyze complexity

State that the brute-force approach takes O(n) time per check, so O(n) overall since there are at most 4 combinations. Space is O(n) for the new strings.

5. Discuss optimization

Mention that you can avoid constructing strings by comparing characters directly, and that there might be a more efficient condition-based solution.

Key Points to Mention

Definition of palindrome and how to check it efficiently (two-pointer technique).
The four possible concatenations and why order matters.
Time and space complexity of the brute-force approach.
Edge cases: empty strings, odd length (though problem says equal length, but halves may be unequal if length is odd? Actually equal length strings, but length could be odd? Usually 'cut in half' implies even length, but clarify).
Potential optimization: checking if the halves themselves have certain properties to avoid full string construction.
Communication: explaining the thought process clearly and asking clarifying questions.

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