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`

.

Solution:

Time complexity: O(N)

Space complexity: O(LogN)