| # LeetCode 5: Longest Palindromic Substring | |
| ## Abstract model | |
| Among all contiguous substrings that read identically from left to right and | |
| right to left, maximize the substring length. The verification case transforms | |
| the input with separators, applies Manacher's linear-time radius algorithm, | |
| and copies one maximum palindrome to a caller-provided output buffer. | |
| ## Problem statement | |
| Given a string `s`, return a longest palindromic substring. If several longest | |
| answers exist, any one may be returned. | |
| ## Constraints | |
| - $1 \le |s| \le 1000$. | |
| - `s` contains only digits and English letters. | |
| - The verification output buffer has capacity $|s|+1$ including its terminator. | |
| ## Source | |
| [LeetCode 5, "Longest Palindromic Substring"](https://leetcode.com/problems/longest-palindromic-substring/). | |