{

public:

bool isPalindrome(string s)

{

int left = 0;

int right = s.length() - 1;

auto isLetterOrDig = [](char c) -> bool {

if (c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9') return true;

return false;

};

while (left < right) {

while (left < s.length() && !isLetterOrDig(s[left])) {

left++;

}

while (right >= 0 && !isLetterOrDig(s[right])) {

right--;

}

if (left < right && std::tolower(s[left++]) != std::tolower(s[right--])) {

return false;

}

}

return true;

}

{

Solution s;

assert(s.isPalindrome("abcba"));

assert(!s.isPalindrome("abcb"));

assert(s.isPalindrome("amanaplanacanalpanama"));

assert(s.isPalindrome("A man, a plan, a canal: Panama"));

assert(!s.isPalindrome("race a car"));

assert(s.isPalindrome(""));

assert(s.isPalindrome(" "));

return 0;