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.

 

 to see which companies asked this question

bool isPalindrome(string s) {    string::iterator iter1 = s.begin();    string::iterator iter2 = s.end() - 1;    while (iter1 <= iter2)    {        if (!isalpha(*iter1) && !isdigit(*iter1)) {            iter1++;            continue;        }                    if (!isalpha(*iter2) && !isdigit(*iter2)) {            iter2--;            continue;        }        char c1 = tolower(*iter1);        char c2 = tolower(*iter2);        if (c1 != c2)            return false;        iter1++;        iter2--;    }    return true;}