Separate the Digits in an Array
<p>Given an array of positive integers <code>nums</code>, return <em>an array </em><code>answer</code><em> that consists of the digits of each integer in </em><code>nums</code><em> after separating them in <strong>the same order</strong> they appear in </em><code>nums</code>.</p>

<p>To separate the digits of an integer is to get all the digits it has in the same order.</p>

<ul>
	<li>For example, for the integer <code>10921</code>, the separation of its digits is <code>[1,0,9,2,1]</code>.</li>
</ul>

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

<pre>
<strong>Input:</strong> nums = [13,25,83,77]
<strong>Output:</strong> [1,3,2,5,8,3,7,7]
<strong>Explanation:</strong> 
- The separation of 13 is [1,3].
- The separation of 25 is [2,5].
- The separation of 83 is [8,3].
- The separation of 77 is [7,7].
answer = [1,3,2,5,8,3,7,7]. Note that answer contains the separations in the same order.
</pre>

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

<pre>
<strong>Input:</strong> nums = [7,1,3,9]
<strong>Output:</strong> [7,1,3,9]
<strong>Explanation:</strong> The separation of each integer in nums is itself.
answer = [7,1,3,9].
</pre>

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

<ul>
	<li><code>1 &lt;= nums.length &lt;= 1000</code></li>
	<li><code>1 &lt;= nums[i] &lt;= 10<sup>5</sup></code></li>
</ul>
Array; Simulation
class Solution {
    public int[] separateDigits(int[] nums) {
        List<Integer> res = new ArrayList<>();
        for (int x : nums) {
            List<Integer> t = new ArrayList<>();
            for (; x > 0; x /= 10) {
                t.add(x % 10);
            }
            Collections.reverse(t);
            res.addAll(t);
        }
        int[] ans = new int[res.size()];
        for (int i = 0; i < ans.length; ++i) {
            ans[i] = res.get(i);
        }
        return ans;
    }
}