2625. Flatten Deeply Nested Array

Medium

168

9

Given a **multi-dimensional** array `arr`

and a depth `n`

, return a **flattened** version of that array.

A **multi-dimensional** array is a recursive data structure that contains integers or other **multi-dimensional** arrays.

A **flattened** 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 is less than `n`

. The depth of the elements in the first array are considered to be `0`

.

Please solve it without the built-in `Array.flat`

method.

**Example 1:**

Inputarr = [1, 2, 3, [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]] n = 0Output[1, 2, 3, [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]]ExplanationPassing 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.

**Example 2:**

Inputarr = [1, 2, 3, [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]] n = 1Output[1, 2, 3, 4, 5, 6, 7, 8, [9, 10, 11], 12, 13, 14, 15]ExplanationThe subarrays starting with 4, 7, and 13 are all flattened. This is because their depth of 0 is less than 1. However [9, 10, 11] remains unflattened because its depth is 1.

**Example 3:**

Inputarr = [[1, 2, 3], [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]] n = 2Output[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]ExplanationThe maximum depth of any subarray is 1. Thus, all of them are flattened.

**Constraints:**

`0 <= count of numbers in arr <= 10`

^{5}`0 <= count of subarrays in arr <= 10`

^{5}`maxDepth <= 1000`

`-1000 <= each number <= 1000`

`0 <= n <= 1000`

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