LeetCode63|香山碧云寺云碧山香

示例 1:

输入: "A man, a plan, a canal: Panama"
输出: true
示例 2:

输入: "race a car"
输出: false

public class IsPalindromeTest {
    public static void main(String[] args) {
        String str = "A man, a plan, a canal: Panama";
        boolean palindrome = isPalindrome2(str);
        System.out.println("palindrome = " + palindrome);
    }

    public static boolean isPalindrome(String s) {
        if (s == null || s.length() == 0) {
            return true;
        }
        char[] chars = s.toCharArray();
        StringBuilder stringBuilder = new StringBuilder(chars.length);
        for (char c : chars
        ) {
            if (c >= 'A' && c <= 'Z' || c >= 'a' && c <= 'z' || c >= '0' && c <= '9') {
                stringBuilder.append(c);
            }
        }

        char[] array = stringBuilder.toString().toLowerCase().toCharArray();
        int i = 0;
        int j = array.length - 1;
        while (i < j) {
            if (array[i] != array[j]) {
                return false;
            }
            i++;
            j--;
        }
        return true;
    }

    public static boolean isPalindrome2(String s) {
        if (s == null || s.length() == 0) {
            return true;
        }
        char[] chars = s.toLowerCase().toCharArray();
        int i = 0;
        int j = chars.length - 1;
        while (i < j) {
            if (!Character.isLetterOrDigit(chars[i])) {
                i++;
                continue;
            }
            if (!Character.isLetterOrDigit(chars[j])) {
                j--;
                continue;
            }
            if (chars[i] != chars[j]) {
                return false;
            } else {
                i++;
                j--;
            }
        }

        return true;
    }

}