What is the optimal time complexity of solving Merge K Sorted Lists?

The optimized solution achieves a time complexity of O(n) by using sorting, mathematical shortcuts, or hash table lookups.

What is the auxiliary space complexity for Merge K Sorted Lists?

The space complexity is O(1) since we only use a minimal/constant amount of extra memory for tracking variables (or auxiliary space if dynamic structures are allocated).

What are the typical edge cases we must handle in Merge K Sorted Lists?

Key edge cases include empty collections, negative or large bounds causing integer overflow, arrays with only one element, or inputs where target criteria are not met.

How can we optimize the brute force approach for Merge K Sorted Lists?

Brute force methods often inspect all possible combinations. We optimize this by sorting the input list to enable binary search, or tracking processed items in a set to avoid redundant nested loop lookups.

Back to Practice Dashboard

Top 150 InterviewEasy

Merge K Sorted Lists

Learn how to solve the 'Merge K Sorted Lists' problem. This detailed resource details brute force and optimized approaches.

Mode Selected

Problem Statement

Easy

You are given an array of k linked-lists lists, each linked-list is sorted in ascending order.

Merge all the linked-lists into one sorted linked-list and return it.

The linked lists are represented as a list of Python lists. Implement a function mergeKLists(lists: list) -> list that returns the merged sorted list.

Constraints

•k == lists.length
•0 <= k <= 10000
•0 <= lists[i].length <= 500
•-10000 <= lists[i][j] <= 10000
•lists[i] is sorted in ascending order
•The sum of lists[i].length will not exceed 10000

Examples

Example 1

Input

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

Output

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

Explanation

Merging [1,4,5], [1,3,4], and [2,6] gives [1,1,2,3,4,4,5,6].

Example 2

Input

[]

Output

[]

Explanation

No lists to merge, so the result is empty.

Example 3

Input

[[]]

Output

[]

Explanation

One empty list results in an empty merged list.

Need a Hint?

Analyze the input constraints. Try sorting first (O(n log n)) or using a hash map/set to track seen elements in O(n) time.

Edge Cases to Watch

Empty list or null input variables
Single item lists/arrays
Extremely large input bounds causing integer or stack overflow

Ready to Solve?

Open the problem in PyRun's browser-based Python editor. Your code runs fully offline — no server required.

Open in Editor