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--) { while(i < j && !isalnum(s[i])) i++; while(i < j && !isalnum(s[j])) j--; if(i < j && tolower(s[i]) != tolower(s[j])) return false; } return true; } };