[Lintcode] Valid palindrome Validating palindrome strings

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

Notice

Are you consider that the string might is empty? This was a good question to ask during a interview.

For the purpose of this problem, we define empty string as valid palindrome.

Has you met this question in a real interview? Example

"A man, a plan, a canal: Panama"is a palindrome.

"race a car"is not a palindrome.

Challenge

O (n) time without extra memory.

Leetcode on the original topic, please see my previous blog valid palindrome.

Solution One:

classSolution { Public:    /** * @param s a string * @return Whether The string is a valid palindrome*/    BOOLIspalindrome (string&s) {intleft =0, right = S.size ()-1;  while(Left <Right ) {            if(!isalnum (S[left)) + +Left ; Else if(!isalnum (S[right]))--Right ; Else if((S[left] + +-'a') % +! = (S[right] + +-'a') % +)return false; Else {                ++left; --Right ; }        }        return true; }    BOOLIsalnum (Charc) {if(c >='a'&& C <='Z')return true; if(c >='A'&& C <='Z')return true; if(c >='0'&& C <='9')return true; return false; }};

Solution Two:

classSolution { Public:    /** * @param s a string * @return Whether The string is a valid palindrome*/    BOOLIspalindrome (string&s) {intleft =0, right = S.size ()-1;  while(Left <Right ) {            if(!isalnum (S[left)) + +Left ; Else if(!isalnum (S[right]))--Right ; Else if((S[left] + +-'a') % +! = (S[right] + +-'a') % +)return false; Else {                ++left; --Right ; }        }        return true; }};

[Lintcode] Valid palindrome Validating palindrome strings