题解 | #合并k个已排序的链表#

# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param lists ListNode类一维数组 
# @return ListNode类
#
from typing import Optional
class Solution:
    def mergeKLists(self , lists: List[ListNode]) -> ListNode:
        # write code here
        m = len(lists)
        if m == 0: return None
        if m == 1: return lists[0]
        left = self.mergeKLists(lists[: m // 2])
        right = self.mergeKLists(lists[m // 2: ])
        return self.mergeTwoLists(left, right)
    def mergeTwoLists(self, list1: Optional[ListNode], List2: Optional[ListNode]) -> Optional[ListNode]:
        cur = dummy = ListNode(x=0)
        while list1 and List2:
            if list1.val < List2.val:
                cur.next = list1
                list1 = list1.next
            else:
                cur.next = List2
                List2 = List2.next
            cur = cur.next
        cur.next = list1 if list1 else List2
        return dummy.next