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LeetCode-Valid Palindrome

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.

Solution:

 1 public class Solution { 2     public boolean isPalindrome(String s) { 3         if (s.isEmpty()) return true; 4  5         int p1 = 0, p2 = s.length()-1; 6      while (p1<s.length() && !( (s.charAt(p1)>=‘A‘ && s.charAt(p1)<=‘Z‘)  || (s.charAt(p1)>=‘a‘ && s.charAt(p1)<=‘z‘) || (s.charAt(p1)>=‘0‘ && s.charAt(p1)<=‘9‘) ) ) p1++; 7     while (p2>=0 && !( (s.charAt(p2)>=‘A‘ && s.charAt(p2)<=‘Z‘)  || (s.charAt(p2)>=‘a‘ && s.charAt(p2)<=‘z‘) || (s.charAt(p2)>=‘0‘ && s.charAt(p2)<=‘9‘) ) ) p2--; 8  9         while (p1<p2){10             char c1 = s.charAt(p1);11             char c2 = s.charAt(p2);12             if (c1 == c2 || Math.abs((int) c1 - (int) c2) == Math.abs( (int) ‘A‘ - (int) ‘a‘ ) ){13                 p1++;14                 p2--;15             while (p1<s.length() && !( (s.charAt(p1)>=‘A‘ && s.charAt(p1)<=‘Z‘)  || (s.charAt(p1)>=‘a‘ && s.charAt(p1)<=‘z‘) || (s.charAt(p1)>=‘0‘ && s.charAt(p1)<=‘9‘) ) ) p1++;16          while (p2>=0 && !( (s.charAt(p2)>=‘A‘ && s.charAt(p2)<=‘Z‘)  || (s.charAt(p2)>=‘a‘ && s.charAt(p2)<=‘z‘) || (s.charAt(p2)>=‘0‘ && s.charAt(p2)<=‘9‘) ) ) p2--;17        } else return false;18         }19 20         return true;21     }22 }

 

LeetCode-Valid Palindrome