Reverse Linked List ๐ŸŒ‹

Question

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

Example 1:

Input: head = [1,2,3,4,5]
Output: [5,4,3,2,1]

Example 2:

Input: head = [1,2]
Output: [2,1]

Example 3:

Input: head = []
Output: []

Constraints:

  • The number of nodes in the list is the range [0, 5000].
  • -5000 <= Node.val <= 5000

Follow up: A linked list can be reversed either iteratively or recursively. Could you implement both?

Solution

Time Complexity O(2n) -> O(n)

Space Complexity O(n)

Time Complexity O(n)

Space Complexity O(n)

Time Complexity O(n)

Space Complexity O(1)

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