How should I practice Longest Palindromic Substring?

Start by reading the full statement, solve the visible examples, then compare the pattern against related IBM phone screen problems in FastPrep.

Is Longest Palindromic Substring associated with IBM?

FastPrep tags this as a IBM phone screen coding practice problem when the problem catalog has that company and stage context.

Longest Palindromic Substring

IBM● MediumFULLTIMEPHONE SCREEN

Problem statement

Given a string s, return its longest palindromic substring. A substring is a contiguous part of the string, and a palindrome reads the same from left to right and right to left.

If several longest palindromic substrings exist, return the one with the smallest starting index. Compare characters exactly, so uppercase and lowercase letters are different.

Function

longestPalindrome(s: String) → String

Examples

Example 1

s = "babad"return = "bab"

Both bab and aba have length 3. The substring bab starts at index 0, earlier than aba at index 1.

Example 2

s = "cbbd"return = "bb"

The two middle characters form bb, a palindrome of length 2. No longer substring is a palindrome.

Constraints

1 <= s.length <= 1000.
s contains only ASCII English letters and digits.