Count how many length- substrings of a number divide the number itself.
Given a positive integer num, consider every contiguous substring of its decimal representation with length exactly k. For each such substring, treat it as an integer value (leading zeros are allowed in the substring, but they do not change the numeric value).
A substring is called a k-beauty of num if its numeric value is non-zero and it divides num evenly.
Return the number of k-beauty substrings.
You only need to inspect all length- windows in the digit string of num, convert each window to an integer, and test whether it is a non-zero divisor of num.
num.k.Treat num as a decimal string when scanning substrings.
num.1 <= num1 <= k <= number of digits in num0.Example 1
Input
num = 240, k = 2
Output
2
Explanation
The length-2 substrings are 24 and 40. Both divide 240, so the answer is 2.
Example 2
Input
num = 430043, k = 2
Output
2
Explanation
The length-2 substrings are 43, 30, 00, 04, and 43. Only 43 divides 430043, and it appears twice. The 00 and 04 windows are ignored if their numeric value is 0 or not a divisor.
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