Flatten an Arbitrarily Nested List

Medium ⏱ 12 min 57% acceptance ★★★★☆ 4.2

Implement flatten(nested) that returns a single flat list of values from a list that may contain other lists nested to any depth, using recursion.

Examples

Example 1

Input

flatten([1, [2, [3, 4], 5], 6])

Output

[1, 2, 3, 4, 5, 6]

Explanation

Every nested list is recursively expanded in order.

Example 2

Input

flatten([[1], [2, [3]], []])

Output

[1, 2, 3]

Explanation

Empty sublists contribute nothing.

Constraints

nested contains ints and/or lists (nested to any depth).

Topics

RecursionLists

Companies

AmazonWalmart

Hints

Hint 1

For each item, check isinstance(item, list).

Hint 2

If it is a list, extend the result with flatten(item); otherwise append it directly.

← Binary Search, Recursively Palindrome Check via Recursion →

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