# ---
# title: 148. Sort List
# id: problem148
# author: Tian Jun
# date: 2020-10-31
# difficulty: Medium
# categories: Linked List, Sort
# link: <https://leetcode.com/problems/sort-list/description/>
# hidden: true
# ---
# 
# Given the `head` of a linked list, return _the list after sorting it in
# **ascending order**_.
# 
# **Follow up:** Can you sort the linked list in `O(n logn)` time and `O(1)`
# memory (i.e. constant space)?
# 
# 
# 
# **Example 1:**
# 
# ![](https://assets.leetcode.com/uploads/2020/09/14/sort_list_1.jpg)
# 
#     
#     
#     Input: head = [4,2,1,3]
#     Output: [1,2,3,4]
#     
# 
# **Example 2:**
# 
# ![](https://assets.leetcode.com/uploads/2020/09/14/sort_list_2.jpg)
# 
#     
#     
#     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`
# 
# 
## @lc code=start
using LeetCode

## add your code here:
## @lc code=end
