680. Valid Palindrome II

原题链接：https://leetcode.com/problems/valid-palindrome-ii/description/
在做完第一道回文字符串校验题目之后这第二道题目就很简单了：

/**
 * Created by clearbug on 2018/2/26.
 */
public class Solution {

    public static void main(String[] args) {
        Solution s = new Solution();
        System.out.println(s.validPalindrome("abc"));
    }

    public boolean validPalindrome(String s) {
        if (s == null) {
            return false;
        }
        if (s.length() < 2) {
            return true;
        }

        return validPalindromeHelper(s.toCharArray(), 0, s.length() - 1, 1);
    }

    private boolean validPalindromeHelper(char[] chars, int start, int end, int maxDeleteTimes) {
        while (start < end) {
            if (chars[start] != chars[end]) {
                if (maxDeleteTimes > 0) {
                    return validPalindromeHelper(chars, start + 1, end, maxDeleteTimes - 1)
                            || validPalindromeHelper(chars, start, end - 1, maxDeleteTimes - 1);
                } else {
                    return false;
                }
            }
            start++;
            end--;
        }
        return true;
    }
}