[LeetCode]23 合并K个排序链表

题目描述

合并 k 个排序链表，返回合并后的排序链表。请分析和描述算法的复杂度。

示例:

输入:
[
  1->4->5,
  1->3->4,
  2->6
]
输出: 1->1->2->3->4->4->5->6

代码

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

class Solution:
    def mergeKLists(self, lists):
        """
        :type lists: List[ListNode]
        :rtype: ListNode
        """
        import heapq
        h = []
        head = ListNode(-1)
        tmp = head
        for i in range(len(lists)):
            if lists[i] != None:
                heapq.heappush(h, (lists[i].val, i))
        while len(h) != 0:
            _, loc = heapq.heappop(h)
            tmp.next = lists[loc]
            tmp = tmp.next
            lists[loc] = lists[loc].next
            if lists[loc] != None:
                heapq.heappush(h, (lists[loc].val, loc))
        return head.next