680. Valid Palindrome II

This question asks us if a palindrome is valid if it has at most one possible incorrect character. We have a generic is_palindrome function, and if we find that one character doesn’t match, we check either skipping this character on our left side recursion or our right side recursion.

class Solution:
    def validPalindrome(self, s: str) -> bool:
        def is_palindrome(s, i, j):
            while i < j:
                if s[i] != s[j]:
                    return False
                i += 1
                j -= 1
            return True
        
        i = 0
        j = len(s) - 1
        while i < j:
            if s[i] != s[j]:
                return is_palindrome(s, i, j - 1) or is_palindrome(s, i + 1, j)
            i += 1
            j -= 1
        
        return True