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.
class Solution { public: bool isPalindrome(string s) { for (int i = 0, j = s.size() - 1; i < j; i++, j--) { // Move 2 pointers from each end until they collide while (isalnum(s[i]) == false && i < j) i++; // Increment left pointer if not alphanumeric while (isalnum(s[j]) == false && i < j) j--; // Decrement right pointer if no alphanumeric if (toupper(s[i]) != toupper(s[j])) return false; // Exit and return error if not match } return true; } };
