2026-01-10 14:26:29 +0300 MSK

class Solution:
    def shortestPalindrome(self, s: str) -> str:
        reversed_string = s[::-1]
        combined_string = "#".join((s, reversed_string))
        prefix_table = self._kmp_table(combined_string)
        palindrome_length = prefix_table[-1]
        suffix = reversed_string[: len(s) - palindrome_length]
        return suffix + s

    def _kmp_table(self, s: str) -> list[int]:
        prefix_table = [0] * len(s)
        length = 0
        for i in range(1, len(s)):
            while length > 0 and s[i] != s[length]:
                length = prefix_table[length - 1]
            if s[i] == s[length]:
                length += 1
            prefix_table[i] = length
        return prefix_table