合并 k 个排序链表，合并返回合并后的排序排序链表。云服务器请分析和描述算法的链表复杂度。网站模板
示例:
输入:[ 1->4->5,合并 1->3->4, 2->6 ]输出: 1->1->2->3->4->4->5->6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 # Definition for singly-linked list.# class ListNode(object):# def __init__(self, x):# self.val = x# self.next = Noneclass Solution(object): def mergeKLists(self, lists): """ :type lists: List[ListNode] :rtype: ListNode """ #合成一个大的listlist然后排序 lists = [x for x in lists if x] if not lists or all([not x for x in lists]): return head = lists.pop() curr = head while curr.next: curr = curr.next while lists: tmp = lists.pop() curr.next = tmp while tmp.next: tmp = tmp.next curr = tmp if not head or not head.next: return head return self.mergeSort(head) def mergeSort(self, head): if not head.next: return head pre, slow, fast = None, head, head while fast and fast.next: prev, slow, fast = slow, slow.next, fast.next.next prev.next = None left = self.mergeSort(head) right = self.mergeSort(slow) return self.merge(left, right) def merge(self, left, right): if not left: return right if not right: return left if left.val < right.val: res = left res.next = self.merge(left.next, right) else: res = right res.next = self.merge(left, right.next) return res
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