LeetCode125_给定一个字符串_判断是否是回文字符串(只考虑数字和字母_忽略大小写)

/**
 * 给定一个字符串，判断是否是回文字符串(只考虑数字和字母，忽略大小写)
 * <p>
 * Given a string s, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.
 * <p>
 * Example 1:
 * <p>
 * Input: s = "A man, a plan, a canal: Panama"
 * Output: true
 * Explanation: "amanaplanacanalpanama" is a palindrome.
 * <p>
 * Example 2:
 * <p>
 * Input: s = "race a car"
 * Output: false
 * Explanation: "raceacar" is not a palindrome.
 * <p>
 * Constraints:
 * <p>
 * 1 <= s.length <= 2 * 10^5
 * s consists only of printable ASCII characters.
 */
public class _125_ValidPalindrome {

    public static void main(String[] args) {
        String s = "A man, a plan, a canal: Panama";
        System.out.println(isPalindrome(s));
        s = "race a car";
        System.out.println(isPalindrome(s));
        s = "0P";
        System.out.println(isPalindrome(s));
    }

    public static boolean isPalindrome1(String s) {
        char[] chars = s.toLowerCase().toCharArray();
        int l = 0;
        int r = chars.length - 1;
        while (l < r) {
            if (!((chars[l] >= 'a' && chars[l] <= 'z') || (chars[l] >= '0' && chars[l] <= '9'))) {
                l++;
                continue;
            }
            if (!((chars[r] >= 'a' && chars[r] <= 'z') || (chars[r] >= '0' && chars[r] <= '9'))) {
                r--;
                continue;
            }
            if (chars[l] != chars[r]) {
                return false;
            }
            l++;
            r--;
        }
        return true;
    }

    /**
     * LeetCode评论区解法之一
     */
    public static boolean isPalindrome(String s) {
        int l = 0;
        int r = s.length() - 1;
        while (l < r) {
            char chL = s.charAt(l);
            if (!Character.isLetterOrDigit(chL)) {
                l++;
                continue;
            }
            char chR = s.charAt(r);
            if (!Character.isLetterOrDigit(chR)) {
                r--;
                continue;
            }
            if (chL >= 'A' && chL <= 'Z') {
                chL = Character.toLowerCase(chL);
            }
            if (chR >= 'A' && chR <= 'Z') {
                chR = Character.toLowerCase(chR);
            }
            if (chL != chR) {
                return false;
            }
            l++;
            r--;
        }
        return true;
    }

}

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