LeetCode 125 Valid Palindrome

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.

回文字符串，就是指去掉所有标点符合后，只有数字和字符，回文就可以了。

注意正则表达式的使用：

	public boolean isPalindrome(String s) {
		s = s.toLowerCase().replaceAll("[^a-z|^0-9]", "");
		int len = s.length();
		for (int i = 0; i < len; i++) {
			if (s.charAt(i) != s.charAt(len - 1 - i))
				return false;
		}
		return true;
	}