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Merge k Sorted Lists | CodeTutor

Merge k Sorted Lists

Hard

Linked Lists Heap Heap / Priority Queue

Problem

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.

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

Examples

Input: lists = [[1,4,5],[1,3,4],[2,6]]

Output: [1,1,2,3,4,4,5,6]

Merge three sorted lists: [1,4,5] + [1,3,4] + [2,6] = [1,1,2,3,4,4,5,6]

Input: lists = []

Output: []

No lists to merge.

Input: lists = [[]]

Output: []

Single empty list.

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