Duplicate Zeros
<p>Given a fixed-length integer array <code>arr</code>, duplicate each occurrence of zero, shifting the remaining elements to the right.</p>

<p><strong>Note</strong> that elements beyond the length of the original array are not written. Do the above modifications to the input array in place and do not return anything.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> arr = [1,0,2,3,0,4,5,0]
<strong>Output:</strong> [1,0,0,2,3,0,0,4]
<strong>Explanation:</strong> After calling your function, the input array is modified to: [1,0,0,2,3,0,0,4]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> arr = [1,2,3]
<strong>Output:</strong> [1,2,3]
<strong>Explanation:</strong> After calling your function, the input array is modified to: [1,2,3]
</pre>

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

<ul>
	<li><code>1 &lt;= arr.length &lt;= 10<sup>4</sup></code></li>
	<li><code>0 &lt;= arr[i] &lt;= 9</code></li>
</ul>
Array; Two Pointers
func duplicateZeros(arr []int) {
	n := len(arr)
	i, k := -1, 0
	for k < n {
		i, k = i+1, k+1
		if arr[i] == 0 {
			k++
		}
	}
	j := n - 1
	if k == n+1 {
		arr[j] = 0
		i, j = i-1, j-1
	}
	for j >= 0 {
		arr[j] = arr[i]
		if arr[i] == 0 {
			j--
			arr[j] = arr[i]
		}
		i, j = i-1, j-1
	}
}