Shortest Palindrome

Given a string, prepend the fewest characters to the front to make it a palindrome and return the result. This is LeetCode 214: the linear-time approach finds the longest palindromic prefix via a KMP failure function (or rolling hash) over s + separator + reverse(s), then mirrors the remaining suffix onto the front, handling inputs up to 5 * 10^4 lowercase letters. Shortest Palindrome Given a string, prepend the fewest characters to the front to make it a palindrome and return the result. This is LeetCode 214: the linear-time approach finds the longest palindromic prefix via a KMP failure function (or rolling hash) over s + separator + reverse(s), then mirrors the remaining suffix onto the front, handling inputs up to 5 * 10^4 lowercase letters. MLE SWE string palindromes two-pointer hard Frequency Single report Last asked 2026-01-02 Stage onsite-coding Shortest Palindrome You are given a string s. You may add characters only to the front of the string. Return the shortest palindrome you can build this way. Examples Example 1: Input: s = "aacecaaa" Output: aaacecaaa Example 2: Input: s = "abcd" Output: dcbabcd Constraints 0 <= s.length <= 5 * 10^4 s consists of lowercase English letters.