import pytest


def isPalindrome(s: str):
    s = ''.join(ch for ch in s if ch.isalnum()).lower()
    if s == '':
        return True
    lens = len(s)
    p, q = 0, lens - 1
    while p < lens or q > 0:
        if p >= q:
            return True
        elif s[p] == s[q]:
            p += 1
            q -= 1
        else:
            return False

@pytest.mark.parametrize(
    "s, expect",
    [
        ("", True),
        (".", True),
        ("aa", True),
        ("A man, a plan, a canal: Panama", True),
        ("a123a", False)
    ]
)

def test_cases(s, expect):
    assert isPalindrome(s) == expect