[Leetcode] 0023. Merge k Sorted Lists

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內容目錄

Hard

You are given an array of k linked-lists lists, each linked-list is sorted in ascending order.

Merge all the linked-lists into one sorted linked-list and return it.

Example 1:

Input: lists = [[1,4,5],[1,3,4],[2,6]]
Output: [1,1,2,3,4,4,5,6]
Explanation: The linked-lists are:
[
  1->4->5,
  1->3->4,
  2->6
]
merging them into one sorted list:
1->1->2->3->4->4->5->6

Example 2:

Input: lists = []
Output: []

Example 3:

Input: lists = [[]]
Output: []

Constraints:

k == lists.length
0 <= k <= 10⁴
0 <= lists[i].length <= 500
-10⁴ <= lists[i][j] <= 10⁴
lists[i] is sorted in ascending order.
The sum of lists[i].length will not exceed 10⁴.

Python

				
					# Definition for singly-linked list.
from typing import List, Optional


class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next


class Solution:
    def mergeKLists(self, lists: List[Optional[ListNode]]) -> Optional[ListNode]:
        nodes = []
        head = point = ListNode(0)
        for left in lists:
            while left:
                nodes.append(left.val)
                left = left.next
        for x in sorted(nodes):
            point.next = ListNode(x)
            point = point.next
        return head.next

Hard

Python

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