_125_ValidPalindrome.java

package leetcode_1To300;

/**
 * 本代码来自 Cspiration，由 @Cspiration 提供
 * 题目来源：http://leetcode.com
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 * - 版权所有，转发请注明出处
 */
public class _125_ValidPalindrome {
    /**
     * 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.

     case : "A man, a plan, a canal: Panama"

     time : O(n)
     space : O(1);

     * @param s
     * @return
     */
    public static boolean isPalindrome(String s) {
        if (s == null || s.length() == 0) return true;
        int left = 0;
        int right = s.length() - 1;
        while (left < right) {
            while (left < right && !Character.isLetterOrDigit(s.charAt(left))) {
                left++;
            }
            while (left < right && !Character.isLetterOrDigit(s.charAt(right))) {
                right--;
            }
            if (Character.toLowerCase(s.charAt(left)) != Character.toLowerCase(s.charAt(right))) {
                return false;
            }
            left++;
            right--;
        }
        return true;
    }
}