[LeetCode] 680. Valid Palindrome II_Easy tag: Two Pointers

Posted 2020-12-29

Given a non-empty string s, you may delete at most one character. Judge whether you can make it a palindrome.

Example 1:

Input: "aba"
Output: True

 

Example 2:

Input: "abca"
Output: True
Explanation: You could delete the character ‘c‘.

 

Note:

1. The string will only contain lowercase characters a-z. The maximum length of the string is 50000.

 

题目思路就是正常的用two pointers去遍历s, 然后如果有不一样的, 要么把l + = 1, 要么把r -= 1 , 然后如果这两个中有一个是palindrome, 那么就符合.

 

Code:

class Solution:
    def palindrome2(self, s): # len(s) >= 1
        l, r = 0, len(s)-1
        def helper(l, r, s):
            while l < r:
                if s[l] == s[r]:
                    l += 1
                    r -=  1
                else:
                    return False
            return True
        while l <r:
            if s[l] == s[r]:
                l += 1
                r -= 1
            else:
                return helper(l+1, r, s) or helper(l, r-1, s)
        return True