[leetcode]125. Valid Palindrome@Java解题报告

本文链接：https://blog.youkuaiyun.com/zjkC050818/article/details/76117745

本文介绍了一个判断字符串是否为回文的有效方法，考虑了只包含字母和数字的情况，并忽略大小写。通过双指针技巧，该算法能高效地解决LeetCode上的有效回文问题。

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https://leetcode.com/problems/valid-palindrome/#/description

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.

package go.jacob.day726;

/**
 * 125. Valid Palindrome
 * 
 * @author Jacob
 *
 */
public class Demo1 {
	/*
	 * 476 / 476 test cases passed. Status: Accepted Runtime: 9 ms
	 */
	public boolean isPalindrome(String s) {
		if (s.isEmpty()) {
			return true;
		}
		//申请两个指针
		int left = 0, right = s.length() - 1;
		char cLeft, cRight;
		while (left < right) {
			cLeft = s.charAt(left);
			cRight = s.charAt(right);
			//Character有现成的isLetterOrDigit()方法，所以不需要自己编写相应函数
			if (!Character.isLetterOrDigit(cLeft))
				left++;
			else if (!Character.isLetterOrDigit(cRight))
				right--;
			else {
				if (Character.toLowerCase(cLeft) != Character.toLowerCase(cRight))
					return false;
				left++;
				right--;
			}
		}
		return true;

	}

}