【Leetcode】Valid Palindrome

题目链接：https://leetcode.com/problems/valid-palindrome/

题目：

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

For example,
"A man, a plan, a canal: Panama" is a palindrome.
"race a car" is not a palindrome.

Note:
Have you consider that the string might be empty? This is a good question to ask during an interview.

For the purpose of this problem, we define empty string as valid palindrome.

算法：

public boolean isDecent(char c) {
		if (Character.isAlphabetic(c) || Character.isDigit(c)) {
			return true;
		} else
			return false;
	}

	public boolean isPalindrome(String s) {
		char c[] = s.toLowerCase().toCharArray();
		int i = 0, j = c.length - 1;
		while (i < j) {
			if (isDecent(c[i]) && isDecent(c[j])) {
				if (c[i] == c[j]) {
					i++;
					j--;
				} else {
					return false;
				}
			}
			if (!isDecent(c[i])) {
				i++;
			}
			if (!isDecent(c[j])) {
				j--;
			}
		}
		return true;
	}