214. Shortest Palindrome

Problem Link

Description

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You are given a string s. You can convert s to a palindrome by adding characters in front of it.

Return the shortest palindrome you can find by performing this transformation.

 

Example 1:

Input: s = "aacecaaa"
Output: "aaacecaaa"

Example 2:

Input: s = "abcd"
Output: "dcbabcd"

 

Constraints:

• 0 <= s.length <= 5 * 104
• s consists of lowercase English letters only.

Solution

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Python3

class Solution:
    def shortestPalindrome(self, s: str) -> str:
        r = s[::-1]
        for i in range(len(s) + 1):
            if s.startswith(r[i:]):
                return r[:i] + s