680. Valid Palindrome II

Problem Link

Description

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Given a string s, return true if the s can be palindrome after deleting at most one character from it.

 

Example 1:

Input: s = "aba"
Output: true

Example 2:

Input: s = "abca"
Output: true
Explanation: You could delete the character 'c'.

Example 3:

Input: s = "abc"
Output: false

 

Constraints:

• 1 <= s.length <= 105
• s consists of lowercase English letters.

Solution

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Python3

class Solution:
    def validPalindrome(self, s: str) -> bool:
        valid = True
        n = len(s)
        i, j = 0, n - 1
        
        @cache
        def isPalindrome(i, j):
            nonlocal valid
            
            while i < j:
                if s[i] == s[j]:
                    i += 1
                    j -= 1
                else:
                    if valid:
                        valid = False
                        return isPalindrome(i + 1, j) or isPalindrome(i, j - 1)
                    else:
                        return False
        
        
            return i >= j
        
        return isPalindrome(i, j)