[LeetCode] 680. Valid Palindrome II 验证回文字符串 II

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.

125. Valid Palindrome 的拓展，给定一个非空字符串，最多可删除1个字符，判断是否可以变成回文。

解法：还是从首尾两边开始比较，如果匹配就移动指针继续比较。当遇到不匹配的时候，删除左边的字符或者右边的字符，只要有一种能匹配就继续。

Python：

class Solution(object):
    def validPalindrome(self, s):
        """
        :type s: str
        :rtype: bool
        """
        def validPalindrome(s, left, right):
            while left < right:
                if s[left] != s[right]:
                    return False
                left, right = left+1, right-1
            return True
        
        left, right = 0, len(s)-1
        while left < right:
            if s[left] != s[right]:
                return validPalindrome(s, left, right-1) or validPalindrome(s, left+1, right)
            left, right = left+1, right-1
        return True

C++：

class Solution {
public:
    bool validPalindrome(string s) {
        int left = 0, right = s.length() - 1;
        while (left < right) {
            if (s[left] != s[right]) {
                return validPalindrome(s, left, right - 1) || validPalindrome(s, left + 1, right);
            }
            ++left, --right;
        }
        return true;
    }

private:
    bool validPalindrome(const string& s, int left, int right) {
        while (left < right) {
            if (s[left] != s[right]) {
                return false;
            }
            ++left, --right;
        }
        return true;
    }
};

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[LeetCode] 125. Valid Palindrome 验证回文字符串

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