【Leetcode】Valid Palindrome

题目链接：https://leetcode.com/problems/valid-palindrome/

题目：

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.

算法：

[java] view plain copy

 

1. public boolean isDecent(char c) {  
2.         if (Character.isAlphabetic(c) || Character.isDigit(c)) {  
3.             return true;  
4.         } else  
5.             return false;  
6.     }  
7.   
8.     public boolean isPalindrome(String s) {  
9.         char c[] = s.toLowerCase().toCharArray();  
10.         int i = 0, j = c.length - 1;  
11.         while (i < j) {  
12.             if (isDecent(c[i]) && isDecent(c[j])) {  
13.                 if (c[i] == c[j]) {  
14.                     i++;  
15.                     j--;  
16.                 } else {  
17.                     return false;  
18.                 }  
19.             }  
20.             if (!isDecent(c[i])) {  
21.                 i++;  
22.             }  
23.             if (!isDecent(c[j])) {  
24.                 j--;  
25.             }  
26.         }  
27.         return true;  
28.     }