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leetcode-cn/problem (English)/扁平化嵌套数组(English) [flatten-deeply-nested-array].html

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+<p>Write a function that accepts a <strong>multi-dimensional</strong> array&nbsp;<code>arr</code>&nbsp;and a depth <code>n</code>, and returns a&nbsp;<strong>flattened</strong>&nbsp;version of that array.</p>
+
+
+
+<p>A <strong>multi-dimensional</strong>&nbsp;array is a recursive data structure that contains integers or other&nbsp;<strong>multi-dimensional</strong>&nbsp;arrays.</p>
+
+
+
+<p>A&nbsp;<strong>flattened</strong>&nbsp;array is a version of that array with some or all of the sub-arrays removed and replaced with the actual elements in that sub-array. This flattening operation should only be done if the current depth of nesting&nbsp;is greater than&nbsp;<code>n</code>. The depth of the elements in the first array are considered to be&nbsp;0.</p>
+
+
+
+<p>Please solve it without the built-in&nbsp;<code>Array.flat</code> method.</p>
+
+
+
+<p>&nbsp;</p>
+
+<p><strong class="example">Example 1:</strong></p>
+
+
+
+<pre>
+
+<strong>Input</strong>
+
+arr = [1, 2, 3, [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]]
+
+n = 0
+
+<strong>Output</strong>
+
+[1, 2, 3, [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]]
+
+
+
+<strong>Explanation</strong>
+
+Passing a depth of n=0 will always result in the original array. This is because the smallest possible depth of a subarray (0) is not less than n=0. Thus, no subarray should be flattened. </pre>
+
+
+
+<p><strong class="example">Example 2:</strong></p>
+
+
+
+<pre>
+
+<strong>Input</strong>
+
+arr = [1, 2, 3, [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]]
+
+n = 1
+
+<strong>Output</strong>