Linked List Pairwise Rotation

MediumPython

Problem

How would you pairwise rotate or swap the elements in a linked list?

Implement pairwise_swap(head) to swap adjacent nodes by changing links, not node values. The input is a singly linked list, and the output is its new head. For grading, linked lists are represented as arrays of values before and after serialization.

Constraints

0 <= number of nodes <= 1000
Node values are integers
The list is singly linked
The algorithm must not create replacement nodes for the input elements
The relative order within each adjacent pair is reversed

Function Signature

def pairwise_swap(head):

CodePython 3

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