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.
**Note:** For this problem, linked lists are represented as arrays for simplicity.
Example 1
Input:lists = [[1,4,5],[1,3,4],[2,6]]
Output:[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.