Merge K Sorted Linked Lists

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Your question is Merge K Sorted Linked Lists. Start with the requirements on the right.

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Problem

At Meta, imagine multiple pre-sorted event streams need to be combined into one ordered feed. Given k sorted singly linked lists, merge them into one sorted linked list and return its head.

Formal Specification

Implement a function that takes lists, where lists[i] is the head of a sorted singly linked list or null. Each node contains an integer value and a next pointer. Return the head of a new merged sorted linked list formed by reusing the existing nodes.

Constraints

0 <= k <= 10^4
0 <= total number of nodes <= 10^5
-10^4 <= Node.val <= 10^4
Each linked list is sorted in non-decreasing order

Function Signature

def merge_k_lists(lists):

Your solutionPython 3

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