Reverse Linked List

Reverse Linked List

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

Examples

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 in the range [0, 5000].
• -5000 <= Node.val <= 5000

Expected Complexity

• Time: O(n)
• Space: O(1) for iterative, O(n) for recursive