题目大意

1. 验证回文字符串 Ⅱ
   给定一个非空字符串 s，最多删除一个字符。判断是否能成为回文字符串。

   解题思路

   双指针的方法解决

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