Given the head of a linked list, return the list after sorting it in ascending order.

Example 1

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

Example 2

Input: head = [-1,5,3,4,0]
Output: [-1,0,3,4,5]

Example 3

Input: head = []
Output: []

Constraints

• The number of nodes in the list is in the range [0, 5 * 10⁴].
• -10⁵ <= Node.val <= 10⁵

Follow-up: Can you sort the linked list in O(n log n) time and O(1) memory (i.e., constant space)?

How the tests work: lists are written as arrays — [1,2,3] is the chain 1 → 2 → 3. Your function receives real ListNode objects, and the list you return is read back into an array.