心路历程：

这道题通过很简单，但是如果想要用O(1)的空间复杂度+O(nlogn)的时间复杂度的话，可能得需要双指针+快排的思路。

解法：遍历模拟

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def sortList(self, head: Optional[ListNode]) -> Optional[ListNode]:
        res = []
        t1 = head
        while t1:
            res.append(t1.val)
            t1 = t1.next
        res.sort()
        t2 = head
        c = 0
        while t2:
            t2.val = res[c]
            c+=1
            t2 = t2.next
        return head