Leetcode 125: Valid Palindrome

Posted 2020-10-22 Keep walking

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.

 

 1 public class Solution {
 2     public bool IsPalindrome(string s) {
 3         if (s == null || s.Length < 2) return true;
 4         
 5         int i = 0, j = s.Length - 1;
 6         
 7         while (i < j)
 8         {
 9             while (i < j && !Char.IsLetterOrDigit(s[i]))
10             {
11                 i++;
12             }
13                    
14             while (i < j && !Char.IsLetterOrDigit(s[j]))
15             {
16                 j--;
17             }
18                    
19             if (Char.ToLower(s[i]) != Char.ToLower(s[j])) return false;
20             i++;
21             j--;
22         }
23         
24         return true;
25     }
26 }