LeetCode_125. Valid Palindrome

125. Valid Palindrome

Easy

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

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

Example 1:

Input: "A man, a plan, a canal: Panama"
Output: true

Example 2:

Input: "race a car"
Output: false

package leetcode.easy;

public class ValidPalindrome {
	@org.junit.Test
	public void test() {
		System.out.println(isPalindrome("A man, a plan, a canal: Panama"));
		System.out.println(isPalindrome("race a car"));
	}

	public boolean isPalindrome(String s) {
		s = s.trim().toLowerCase();
		char[] chs = s.toCharArray();
		int count = 0;
		for (int i = 0; i < chs.length; i++) {
			if ((chs[i] >= '0' && chs[i] <= '9') || (chs[i] >= 'a' && chs[i] <= 'z')) {
				chs[count] = chs[i];
				count++;
			}
		}
		for (int i = 0; i < count / 2; i++) {
			if (chs[i] != chs[count - i - 1]) {
				return false;
			}
		}
		return true;
	}
}