Return a Longest Palindromic Slice

### Problem Given the string `text`, return a contiguous substring of maximum length whose characters read identically from left to right and from right to left. If several substrings reach that maximum length, any one is acceptable. ### Examples **Example 1** ```text Input: text = "racecarzabba" Output: "racecar" ``` The seven-character palindrome is longer than the four-character palindrome near the end. **Example 2** ```text Input: text = "abaxyzcdc" Output: "cdc" ``` The substring `"aba"` is another acceptable answer: both have length three, and neither can be extended to a longer palindrome in this input. ### Constraints & Assumptions - The string contains between 1 and 1,000 characters, inclusive. - Its characters are English letters and decimal digits. - The returned characters must occupy consecutive positions in the input. A subsequence assembled from separated positions does not qualify. - Compare the characters as given; no case folding or character filtering is requested. - No tie-breaking rule or particular algorithm is required. ### Clarifying Questions to Ask - When two different palindromes have the same maximum length, can either be returned? Yes; there is no preference for the earlier occurrence or a particular spelling. - Does a one-character substring qualify? Yes, including when no longer palindrome exists. ```hint Check the boundary cases An optimal answer can have either an odd or an even number of characters. A method that handles only one of those shapes is incomplete. ``` ### What a Strong Answer Covers - A method that considers both odd-length and even-length palindromes while returning an actual substring. - A reason that every possible longest palindrome is represented among the cases examined. - Correct handling of repeated characters, single-character inputs, and tied maximum lengths. - Time and auxiliary-space bounds, with the returned string accounted for separately. ### Follow-up Questions - What extra state would a substring dynamic-programming approach store, and how would its costs compare? - Can repeated comparisons be shared to obtain a linear-time method? Describe the key reuse rule without imposing a tie-break on the answer.