Valid Palindrome（LintCode）

Valid Palindrome

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

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.

Challenge

O(n) time without extra memory.

深刻体会到了英文的用处。。。题目的中文翻译真是误导人。

 public class Solution {

     /**

      * @param s A string

      * @return Whether the string is a valid palindrome

      */

     public boolean isPalindrome(String s) {

         char[] cs = s.toCharArray();

         int i = 0;

         int j = cs.length - 1;

         while(i<j) {

             while(i<j && !Character.isDigit(cs[i]) && !Character.isLetter(cs[i])) i++;

             while(i<j && !Character.isDigit(cs[j]) && !Character.isLetter(cs[j])) j--;

             if(i >= j) break;

             String ss = cs[i] + "";

             String ss1 = cs[j] + "";

             if(!ss.equalsIgnoreCase(ss1))

                 return false;

             i++;

             j--;

         }

         return true;

     }

 }

巴特西

Valid Palindrome（LintCode）

Valid Palindrome

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