Linked List Coding Problem | Dataford Interview Questions

Airbnb's listing photo carousel stores photo identifiers in a singly linked list. Given the list L0 -> L1 -> ... -> Ln, reorder it in place as L0 -> Ln -> L1 -> Ln-1 -> L2 -> ....

Return the head of the reordered linked list. Do not create new list nodes. The list may be modified by changing node links.

Formal Specification

The input is the head of a singly linked list, where each node has an integer val and a next pointer. The output is the head of the same nodes in the required alternating order. For examples and test cases, lists are represented as arrays, and the test harness converts each array to a linked list before calling the function.

Constraints

1 <= number of nodes <= 5 * 10^4
-10^5 <= node.val <= 10^5
Node values are not necessarily unique.
Use the original nodes without creating replacement nodes.
Use O(1) auxiliary space.

Function Signature

def reorder_list(head):

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