在 O(n log n) 時間複雜度和常數級空間複雜度下，對連結串列進行排序。

示例 1:

輸入: 4->2->1->3
輸出: 1->2->3->4

示例 2:

輸入: -1->5->3->4->0
輸出: -1->0->3->4->5

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def sortList(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        data = []
        while head:
            data.append(head.val)
            head = head.next
        data.sort()
        ptr = ListNode(0)
        ptr1 = ptr
        for item in data:
            ptr.next = ListNode(item)
            ptr = ptr.next
        return ptr1.next