Longest Palindromic Substr 25 XP Medium

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Find the longest palindromic substring. The expand-around-center approach is elegant and uses O(1) space.

# For each center (and between chars):
#   Expand outward while chars match
#   Track the longest palindrome found
# O(n²) time, O(1) space

Each character is a center for odd-length palindromes. Each pair of adjacent chars is a center for even-length palindromes.

💡 Pro tip: Understand this problem deeply — don't just memorize the code. Try explaining the approach out loud as if teaching a friend. If you can explain it simply, you truly understand it!

📋 Instructions

Find the longest palindromic substring of 'babad'. Print its length.

Helper: expand(l, r) while l>=0 and r<n and s[l]==s[r]. Try both odd and even centers.

🧪 Test Cases

Input

len(longestPalindrome('babad'))

Expected

3

Test case 1

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main.py

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Output

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