125. Valid Palindrome

原题链接：https://leetcode.com/problems/valid-palindrome/description/
校验回文字符串，题目较为简单：

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

    public static void main(String[] args) {
        Solution s = new Solution();
        System.out.println(s.isPalindrome("0P"));
        System.out.println(s.isPalindrome("ab"));
        System.out.println(s.isPalindrome("aba"));
        System.out.println(s.isPalindrome("A man, a plan, a canal: Panama"));
        System.out.println(s.isPalindrome("race a car"));
    }

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

        s = s.toLowerCase();

        char[] sCharArr = s.toCharArray();
        for (int i = 0, j = sCharArr.length - 1; i < j; i++, j--) {
            while (i < j && !(sCharArr[i] >= 'a' && sCharArr[i] <= 'z') && !(sCharArr[i] >= '0' && sCharArr[i] <= '9')) {
                i++;
            }
            while (i < j &&!(sCharArr[j] >= 'a' && sCharArr[j] <= 'z') && !(sCharArr[j] >= '0' && sCharArr[j] <= '9')) {
                j--;
            }
            if (sCharArr[i] != sCharArr[j]) {
                return false;
            }
        }
        return true;
    }
}