2025-08-18 15:43:22 +0000 UTC

class Solution:
    def divisorSubstrings(self, num: int, k: int) -> int:
        digits = []
        cur_num = num
        while cur_num > 0:
            digits.append(cur_num % 10)
            cur_num //= 10
        digits.reverse()
        length = len(digits)
        if length < k:
            return 0
        cur_sum = 0
        res = 0
        for i in range(k):
            cur_sum += digits[i] * (10 ** (k - i - 1))
        if num % cur_sum == 0:
            res += 1 
        i = k
        while i < length:
            cur_sum -= digits[i - k] * (10 ** (k - 1))
            cur_sum = cur_sum * 10 + digits[i]
            if cur_sum != 0 and num % cur_sum == 0:
                res += 1
            i += 1
        return res