Coding: Linked List Merge | Dataford Interview Questions

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Problem

A GE HealthCare Edison imaging workflow may maintain sorted linked lists of work items from two processing streams. Given the heads of two singly linked lists sorted in nondecreasing order, merge them into one sorted linked list.

Formal Specification

Implement merge_sorted_lists(l1, l2), where l1 and l2 are either ListNode objects or None. Each ListNode has an integer val field and a next field. Return the head of the merged list. Reuse the existing nodes rather than creating nodes for every output value. If values are equal, either source list may be selected first.

For the JSON test cases, each input list is represented by an array of node values, and the expected result is the merged array of values.

Constraints

0 <= len(l1), len(l2) <= 10^5
-10^9 <= node.val <= 10^9
Each input list is sorted in nondecreasing order
Input nodes form finite, acyclic singly linked lists

Function Signature

def merge_sorted_lists(l1, l2):