Reverse Linked List

Easy~15 min

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

Each node in the list has a val (integer value) and a next pointer to the next node. The last node points to null.

Examples

Example 1
Input: head = [1, 2, 3, 4, 5]
Output: [5, 4, 3, 2, 1]
Explanation: The list 1→2→3→4→5 becomes 5→4→3→2→1 after reversal.
Example 2
Input: head = [1, 2]
Output: [2, 1]
Example 3
Input: head = []
Output: []
Explanation: An empty list remains empty after reversal.

Constraints

  • The number of nodes in the list is in the range [0, 5000]
  • -5000 <= Node.val <= 5000
  • Expected time complexity: O(n)
Code
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Output

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