5. Longest Palindromic Substring
Given a string s, return the longest palindromic substring in s.
Example 1:
Input: s = "babad" Output: "bab" Explanation: "aba" is also a valid answer.
Example 2:
Input: s = "cbbd" Output: "bb"
Constraints:
1 <= s.length <= 1000sconsist of only digits and English letters.
Two PointersStringDynamic ProgrammingManacher
Hints
Hint 1
How can we reuse a previously computed palindrome to compute a larger palindrome?
Hint 2
If “aba” is a palindrome, is “xabax” a palindrome? Similarly is “xabay” a palindrome?
Hint 3
Complexity based hint:
If we use brute-force and check whether for every start and end position a substring is a palindrome we have O(n^2) start - end pairs and O(n) palindromic checks. Can we reduce the time for palindromic checks to O(1) by reusing some previous computation.
If we use brute-force and check whether for every start and end position a substring is a palindrome we have O(n^2) start - end pairs and O(n) palindromic checks. Can we reduce the time for palindromic checks to O(1) by reusing some previous computation.
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