Valid Palindrome

最新推荐文章于 2024-01-04 12:53:14 发布

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最新推荐文章于 2024-01-04 12:53:14 发布

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本文介绍了一种用于判断字符串是否为回文的有效算法。该算法忽略大小写和非字母数字字符，仅考虑字母数字部分来判断字符串是否正反相同。特别地，文章中还讨论了空字符串的情况，并将其视为有效的回文。

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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.

参杂噪音的回文判断

public class Solution {
    public boolean isPalindrome(String s) {
		if (s.trim().length() == 0) {
			return true;
		}

		char[] parts = s.trim().toLowerCase().toCharArray();
		int low = 0;
		int high = parts.length - 1;
		while (low < high) {
			while (low < parts.length && !isLetter(parts[low])) {
				low++;
			}
			while (high >= 0 && !isLetter(parts[high])) {
				high--;
			}
			if (low >= high) {
				return true;
			} else if (parts[low] != parts[high]) {
				return false;
			} else {
				low++;
				high--;
			}

		}
		return true;

	}

	public boolean isLetter(char input) {
		return (input >= 'a' && input <= 'z') || (input >= 'A' && input <= 'Z')
				|| (input >= '0' && input <= '9');
	}
}