leetcode2520: Count the Digits That Divide a Number

### Description

Given an integer num, return the number of digits in num that divide num.

An integer val divides nums if nums % val == 0.

#### Example 1:

Input: num = 7
Output: 1
Explanation: 7 divides itself, hence the answer is 1.

#### Example 2:

Input: num = 121
Output: 2
Explanation: 121 is divisible by 1, but not 2. Since 1 occurs twice as a digit, we return 2.

#### Example 3:

Input: num = 1248
Output: 4
Explanation: 1248 is divisible by all of its digits, hence the answer is 4.

#### Constraints:

1 <= num <= 109
num does not contain 0 as one of its digits.