Is Convert Doubly Linked List to Array II easy or hard?

Convert Doubly Linked List to Array II is generally considered a medium-level problem. The logic is straightforward traversal, but the question checks understanding of linked list structure and careful pointer iteration.

Convert Doubly Linked List to Array II Python/Java solution

In both Python and Java, iterate through the linked list starting from head and append each node value to a list or array structure. Python typically uses a list with append operations, while Java uses an ArrayList before converting to an array if needed.

How to solve Convert Doubly Linked List to Array II in O(n)?

Iterate through the list starting from the head node. At each step append the current node's value to an array and move to current.next. Stop when the pointer becomes null. This linear traversal ensures O(n) time with a single pass over the nodes.

What is the best approach for Convert Doubly Linked List to Array II?

The best approach is a single-pass traversal of the doubly linked list. Start from the head and follow the next pointer while pushing each node value into an array. This runs in O(n) time and uses O(n) space for the resulting array.

Is Convert Doubly Linked List to Array II asked at Google/Amazon/Meta?

Linked list traversal and structure conversion problems commonly appear in interviews at companies like Amazon, Google, and Meta. Variants of converting linked structures into arrays test understanding of pointer traversal and basic data structure manipulation.

What data structure is used in Convert Doubly Linked List to Array II?

The problem uses a doubly linked list as input and converts it into an array. The traversal relies on the next pointer of each node, while the result is stored sequentially in a dynamic array or list structure.

What is the time complexity of Convert Doubly Linked List to Array II?

The optimal solution runs in O(n) time where n is the number of nodes in the doubly linked list. Each node is visited exactly once during traversal. Space complexity is O(n) because the output array stores all node values.

Description Hints 1 Solution Video 5:28

3294. Convert Doubly Linked List to Array II

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You are given an arbitrary node from a doubly linked list, which contains nodes that have a next pointer and a previous pointer.

Return an integer array which contains the elements of the linked list in order.

Example 1:

Input: head = [1,2,3,4,5], node = 5

Output: [1,2,3,4,5]

Example 2:

Input: head = [4,5,6,7,8], node = 8

Output: [4,5,6,7,8]

Constraints:

The number of nodes in the given list is in the range [1, 500].
1 <= Node.val <= 1000
All nodes have unique Node.val.

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Hint 1

Use the pointer to the previous node to reach the head node.

5:28

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3294. Convert Doubly Linked List to Array II

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