Is Nested Array Generator easy or hard?

Nested Array Generator is considered a medium difficulty problem. The traversal logic is straightforward, but implementing it using generators and handling arbitrary nesting depth requires a good understanding of recursion or stack-based DFS.

Nested Array Generator Python/Java solution

Both Python and JavaScript solutions typically implement a generator that performs depth-first traversal of the nested array. Python uses the `yield` keyword, while JavaScript uses generator functions with `yield` or `yield*` to delegate iteration into nested arrays.

How to solve Nested Array Generator in O(n)?

Traverse the nested array using depth-first search. When encountering an integer, yield it from the generator. When encountering another array, recursively iterate through it or push its elements onto a stack for later processing. Each element is visited once, resulting in O(n) time complexity.

What is the best approach for Nested Array Generator?

The recursive generator approach is usually the cleanest solution. It performs a depth-first traversal of the nested array and yields integers as soon as they are encountered. This method runs in O(n) time and O(d) space, where n is the total number of elements and d is the nesting depth.

Is Nested Array Generator asked at Google/Amazon/Meta?

Problems involving flattening nested structures and implementing iterators or generators appear frequently in interviews at companies like Google, Amazon, and Meta. The exact problem may vary, but the underlying concept of DFS traversal and lazy iteration is commonly tested.

What data structure is used in Nested Array Generator?

The main structures used are recursion stacks or explicit stacks. The recursive solution relies on the call stack to track nested arrays, while the iterative solution uses a stack data structure to simulate depth-first traversal.

What is the time complexity of Nested Array Generator?

The time complexity is O(n) because every integer and nested array element is processed exactly once during traversal. Whether using recursion or a stack-based approach, the algorithm simply walks through the entire nested structure without repeated work.

Description Hints 3 Solution Video 5:01

2649. Nested Array Generator

Medium79.3% acceptance

Given a multi-dimensional array of integers, return a generator object which yields integers in the same order as inorder traversal.

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

inorder traversal iterates over each array from left to right, yielding any integers it encounters or applying inorder traversal to any arrays it encounters.

Example 1:

Input: arr = [[[6]],[1,3],[]]
Output: [6,1,3]
Explanation:
const generator = inorderTraversal(arr);
generator.next().value; // 6
generator.next().value; // 1
generator.next().value; // 3
generator.next().done; // true

Example 2:

Input: arr = []
Output: []
Explanation: There are no integers so the generator doesn't yield anything.

Constraints:

0 <= arr.flat().length <= 10⁵
0 <= arr.flat()[i] <= 10⁵
maxNestingDepth <= 10⁵

Can you solve this without creating a new flattened version of the array?

Hints open one at a time

Hint 1

Generator functions can pass control to another generator function with "yield*" syntax.

Hint 2

Generator functions can recursively yield control to themselves.

Hint 3

You don't need to worry about recursion depth for this problem.

5:01

Still stuck?Read 3 approaches, or watch a walkthrough.

Open solution

2649. Nested Array Generator

Hints open one at a time

Similar problems