class Solution:
    def hasAllCodes(self, s: str, k: int) -> bool:
        num_perms = math.pow(2, k)
        substrings_of_len_k = len(s) - k + 1
        if substrings_of_len_k < num_perms:
            return False
        
        perms = set()

        for i in range(k, len(s)+1):
            perms.add(s[i-k:i])

        return len(perms) == num_perms