Is Merge Two Sorted Lists easy or hard?

Merge Two Sorted Lists is categorized as an Easy problem on most coding platforms. The logic is straightforward once you understand pointer movement in linked lists, making it a common introductory interview problem.

Merge Two Sorted Lists Python/Java solution

Python and Java implementations typically follow the same logic: iterate through both lists, compare current node values, and attach the smaller node to the merged list. Both iterative and recursive versions achieve O(n + m) time complexity.

How to solve Merge Two Sorted Lists in O(n)?

Traverse both lists simultaneously and always attach the smaller node to the result list. Using a dummy head node simplifies the implementation. Because every node from both lists is processed exactly once, the total complexity becomes O(n + m).

What is the best approach for Merge Two Sorted Lists?

The iterative dummy node approach is generally considered the best solution. It merges the two lists in O(n + m) time while using only O(1) extra space. The dummy node simplifies pointer updates and avoids edge cases when initializing the merged list.

Is Merge Two Sorted Lists asked at Google/Amazon/Meta?

Merge Two Sorted Lists appears frequently in coding interviews at companies like Amazon, Google, and Meta. It tests understanding of linked list traversal, pointer manipulation, and algorithmic efficiency using linear-time merging.

What data structure is used in Merge Two Sorted Lists?

The problem uses a singly linked list. The algorithm relies on pointer manipulation to compare nodes from two lists and reconnect them into a single sorted linked list without creating additional data structures.

What is the time complexity of Merge Two Sorted Lists?

The optimal time complexity is O(n + m), where n and m are the lengths of the two linked lists. Each node is visited exactly once while comparing and linking nodes into the final merged list.

Description Solution Video 6:16

21. Merge Two Sorted Lists

Easy68.7% acceptance36 companies

You are given the heads of two sorted linked lists list1 and list2.

Merge the two lists into one sorted list. The list should be made by splicing together the nodes of the first two lists.

Return the head of the merged linked list.

Example 1:

Input: list1 = [1,2,4], list2 = [1,3,4]
Output: [1,1,2,3,4,4]

Example 2:

Input: list1 = [], list2 = []
Output: []

Example 3:

Input: list1 = [], list2 = [0]
Output: [0]

Constraints:

The number of nodes in both lists is in the range [0, 50].
-100 <= Node.val <= 100
Both list1 and list2 are sorted in non-decreasing order.

Asked at top 20 of 36 companies

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Linked List Recursion

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21. Merge Two Sorted Lists

Asked at top 20 of 36 companies

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