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Longest Palindromic Substring (expand around center).

This classic has a clean O(n^2) expand-around-center solution that beats the naive O(n^3). The signal is expanding from every center and handling odd and even lengths separately. Here is the answer.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.

This classic has a clean O(n^2) expand-around-center solution that beats the naive O(n^3). The signal is expanding from every center and handling odd and even lengths separately. Here is the answer.

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