LeetCode Valid Palindrome

原创于 2014-11-03 21:43:55 发布 · 413 阅读

0 ·

CC 4.0 BY-SA版权

OJ 专栏收录该内容

986 篇文章

订阅专栏

本文介绍了一种用于判断字符串是否为回文串的方法，该方法只考虑数字和字母，忽略大小写。通过过滤非字母数字字符并转换为小写，然后与反转后的字符串进行比较来实现。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

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.

题意：给出一个字符中，只考虑数字和字符，忽略大小写，判断是不是回文串

思路：只保留数字，字符，并将字符转换成小写，然后反转与原来的字符串比较

public class Solution {
    public boolean isPalindrome(String s) {
        StringBuilder sb = new StringBuilder(s.length());
        
        for (int i = 0, len = s.length(); i < len; i++) {
            char ch = s.charAt(i);
            if (Character.isLetterOrDigit(ch)) {
                sb.append(Character.toLowerCase(ch));
            }
        }
        
        String tmp = sb.toString();
        return tmp.compareTo(sb.reverse().toString()) == 0;
    }
}