23. Merge k Sorted Lists

Hard

50 Points

Linked List

Divide and Conquer

Heap (Priority Queue)

Merge Sort

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.

Examples

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 linked 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.