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
#
class Solution:
    def mergeKLists(self , lists: List[ListNode]) -> ListNode:
        # write code here

        if not lists:
            return None

        if len(lists) == 1:
            return lists[0]
        else:
            pre0 = lists[0]
            pre1 = self.mergeKLists(lists[1:])
            if(not pre0):
                return pre1
            if(not pre1):
                return pre0

            if(pre0.val > pre1.val):
                phead = pre1
                pre = pre0
            else:
                phead = pre0
                pre = pre1

            pre0 = phead
            while pre0.next:
                while pre and pre0.next.val > pre.val:
                    cur = pre.next
                    pre.next = pre0.next
                    pre0.next = pre
                    pre = cur
                pre0 = pre0.next

            if pre:
                pre0.next = pre
            return phead

写了好久、、、遇到好多BUG，感觉这种都很适合递归，要处理清楚思路，以及注意空的输入！！！

具体太晚了，懒得写了。眠