LeetCode 125. 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.

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.

// two pointer problem

#include <string>
#include <iostream>
using namespace std;

bool isPalindrome(string s) {
if(s.size() <= 1) return true;
int i = 0;
int j = s.size() - 1;
while(i <= j) {
if(isalnum(s[i]) && isalnum(s[j])) {
if(tolower(s[i]) == tolower(s[j])) {
i++;
j--;
continue;
} else {
return false;
}
}
if(!isalnum(s[i])) {i++;}
if(!isalnum(s[j])) {j--;}
}
return true;
}

int main(void) {
string tmp = "A man, a plan, a canal : Panama six";
bool res = isPalindrome(tmp);
cout << res << endl;
}