[Leetcode] 0023. Merge k Sorted Lists

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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 <= 10 ⁴
0 <= lists[i].length <= 500
-10 ⁴ <= lists[i][j] <= 10 ⁴
lists[i] is sorted in ascending order.
The sum of lists[i].length will not exceed 10 ⁴.

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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