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.

class Solution { public: bool isPalindrome(string s) { int left = 0, right = s.size() - 1 ; while (left < right) { if (!isalnum(s[left])) ++left; else if (!isalnum(s[right])) --right; else if ((s[left] + 32 - 'a') 2 != (s[right] + 32 - 'a') % 32) return false; else { ++left; --right; } } return true; } };