LeetCode 680. Valid Palindrome II

原题链接在这里：https://leetcode.com/problems/valid-palindrome-ii/description/

题目：

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.

题解：

当出现错位时，或左或右向内移动一位.

Time Complexity: O(s.length()). Space: O(1).

AC Java:

class Solution {
    public boolean validPalindrome(String s) {
        int l = 0; int r = s.length()-1;
        while(l<r){
            if(s.charAt(l) != s.charAt(r)){
                return isPalindrome(s, l+1, r) || isPalindrome(s, l, r-1);
            }
            l++;
            r--;
        }
        return true;
    }
    
    private boolean isPalindrome(String s, int l, int r){
        while(l<r){
            if(s.charAt(l) != s.charAt(r)){
                return false;
            }
            l++;
            r--;
        }
        return true;
    }
}

AC Python:

class Solution:
    def validPalindrome(self, s: str) -> bool:
        if not s:
            return True

        i, j = 0, len(s) - 1
        while i < j:
            if s[i] != s[j]:
                return self.isPal(s, i + 1, j) or self.isPal(s, i, j - 1)
            i+=1
            j-=1
        return True
    
    def isPal(self, s, l, r):
            while l < r:
                if s[l] != s[r]:
                    return False
                l += 1
                r -= 1
            return True

跟上Valid Palindrome III.

类似Valid Palindrome.