题目描述:
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.
解题思路:
设置两个指针,一个在字符串头部,一个在字符串尾部,分别向中间移动,遇到非字母或数字则继续向中间移动,如两个都为字母或者数字,那么则比较两者是否相同。
代码如下:
public class Solution { public boolean isPalindrome(String s) { int i = 0, j = s.length() - 1; char head, tail; if(j < 0) return true; while(i < j){ head = s.charAt(i); tail = s.charAt(j); if(!Character.isLetterOrDigit(head)){ i++; } if(!Character.isLetterOrDigit(tail)){ j--; } if(Character.isLetterOrDigit(head) && Character.isLetterOrDigit(tail)){ if(Character.toLowerCase(head) != Character.toLowerCase(tail)){ return false; } i++; j--; } } return true; } }
时间: 2024-10-21 13:33:13