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Longest Palindromic Substring

advancedlayer B4 · Two pointers5 tests

Write longestPalindrome(s) returning the longest contiguous slice of s that reads the same in both directions.

  • If several slices tie for longest, returning any one of them is correct
  • Palindromes can have odd length (a centre character) or even length (a centre gap)
  • The empty string yields the empty string; a single character is its own answer
  • Checking every substring is O(n^3) — aim for O(n^2) time and O(1) space

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