# Flatten Deeply Nested Arrays

Medium
60
1
43.4% Acceptance

In this lab, you will be tasked to create a function called `flat` that accepts a deeply nested multi-dimensional array `arr` and a depth value `n`. The function must return a flattened version of that array based on the given depth `n`. The depth at which elements should be flattened depends on the depth value `n`. The depth of the elements in the first array are considered to be `0`. You must solve this problem without using the built-in `Array.flat` method.

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`.

## Examples

Example 1:

``````const arr = [1, 2, 3, [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]];
const n = 0;
const result = flat(arr, n);
console.log(result);
// Output: [1, 2, 3, [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]]``````

Explanation: 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.

Example 2:

``````const arr = [1, 2, 3, [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]];
const n = 1;
const result = flat(arr, n);
console.log(result);
// Output: [1, 2, 3, 4, 5, 6, 7, 8, [9, 10, 11], 12, 13, 14, 15]``````

Explanation: The 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:

``````const arr = [[1, 2, 3], [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]];
const n = 2;
const result = flat(arr, n);
console.log(result);
// Output: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]``````

Explanation: The maximum depth of any subarray is 1. Thus, all of them are flattened.

Constraints:

• `0 <= count of numbers in arr <= 105`
• `0 <= count of subarrays in arr <= 105`
• `maxDepth <= 1000`
• `-1000 <= each number <= 1000`
• `0 <= n <= 1000`