Count the Digits That Divide a Number
<p>Given an integer <code>num</code>, return <em>the number of digits in <code>num</code> that divide </em><code>num</code>.</p>

<p>An integer <code>val</code> divides <code>nums</code> if <code>nums % val == 0</code>.</p>

<p>&nbsp;</p>
<p><strong>Example 1:</strong></p>

<pre>
<strong>Input:</strong> num = 7
<strong>Output:</strong> 1
<strong>Explanation:</strong> 7 divides itself, hence the answer is 1.
</pre>

<p><strong>Example 2:</strong></p>

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

<p><strong>Example 3:</strong></p>

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

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= num &lt;= 10<sup>9</sup></code></li>
	<li><code>num</code> does not contain <code>0</code> as one of its digits.</li>
</ul>
Math
func countDigits(num int) (ans int) {
	for x := num; x > 0; x /= 10 {
		if num%(x%10) == 0 {
			ans++
		}
	}
	return
}