In-Place Linked List Reverse | Dataford Interview Questions

An LG webOS device component stores diagnostic events in a singly linked list ordered from oldest to newest. Reverse the list in place so events can be processed from newest to oldest, without allocating replacement nodes or using a container proportional to the list size.

Implement reverse_list(head), which receives the head of a singly linked list and returns the new head after reversal.

Formal Specification

Each node has an integer value field and a next field that points to another node or None. The input is the head node, or None for an empty list. The function must reuse every existing node, change only next references, and return the new head. In the test cases, linked lists are represented as JSON arrays for readability, and the evaluator converts them to and from linked nodes.

Constraints

0 <= n <= 10^5, where n is the number of nodes
-10^9 <= node.value <= 10^9
The list is singly linked and acyclic
Do not create new list nodes
Do not use an array, stack, or other structure proportional to n

Function Signature

def reverse_list(head):

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