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Reverse a Linked List

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Your question is Reverse a Linked List. Start with the requirements on the right.

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Problem

Given the head of a singly linked list, reverse the list and return the new head.

Implement the reversal in-place by changing the next pointers. Do not create a new list or copy node values.

Formal Specification

  • Input: head, the head node of a singly linked list, or None for an empty list.
  • Output: The head node of the reversed linked list.

Constraints

  • 0 <= number of nodes <= 10^5
  • -10^9 <= node.val <= 10^9
  • The list is singly linked
  • The reversal must be done in-place

Function Signature

def reverse_list(head):
Your solutionPython 3
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