LeetCode --- Valid Palindrome

 1 class Solution {  2 public:  3     bool isPalindrome(string s) {  4         if (s.empty()) return true; // consider empty string as valid palindrome

 5         unsigned int len = s.size();  6         unsigned int beg = 0, end = len - 1;  7         while (beg < end) {  8             while (beg <= end && !isdigit(s[beg]) && !isalpha(s[beg]))  9                 beg++; 10             while (end >= beg && !isdigit(s[end]) && !isalpha(s[end])) 11                 end--; 12             //if (beg == end) return true;

13             if (beg >= end) return true; 14             if (isalpha(s[beg]) && isalpha(s[end])) { 15                 if (toupper(s[beg]) != toupper(s[end])) 16                     return false; 17             } else if (s[beg] != s[end]) { 18                 return false; 19  } 20             beg++; 21             end--; 22  } 23         

24         return true; 25  } 26 };