Find the K-Beauty of a Number

The k-beauty of an integer num is defined as the number of substrings of num when it is read as a string that meet the following conditions:

• It has a length of k.
• It is a divisor of num.

Given integers num and k, return the k-beauty of num.

Note:

• Leading zeros are allowed.
• 0 is not a divisor of any value.

A substring is a contiguous sequence of characters in a string.

Example 1:

Input: num = 240, k = 2
Output: 2
Explanation: The following are the substrings of num of length k:

• "24" from "240": 24 is a divisor of 240.
• "40" from "2*40*": 40 is a divisor of 240. Therefore, the k-beauty is 2.

Example 2:

Input: num = 430043, k = 2
Output: 2
Explanation: The following are the substrings of num of length k:

• "43" from "430043": 43 is a divisor of 430043.
• "30" from "4*30*043": 30 is not a divisor of 430043.
• "00" from "43*00*43": 0 is not a divisor of 430043.
• "04" from "430*04*3": 4 is not a divisor of 430043.
• "43" from "4300*43*": 43 is a divisor of 430043. Therefore, the k-beauty is 2.

Constraints:

• 1 <= num <= 109
• 1 <= k <= num.length (taking num as a string)

SOLUTION:

class Solution:
    def divisorSubstrings(self, num: int, k: int) -> int:
        strnum = str(num)
        n = len(strnum)
        ctr = 0
        for i in range(n - k + 1):
            curr = int(strnum[i:i+k])
            if curr != 0 and num % curr == 0:
                ctr += 1
        return ctr