You are given an array, lists, containing k singly linked lists. Each of these linked lists is individually sorted in ascending order.

Your task is to merge all k linked lists into a single sorted linked list in ascending order and return the merged list.

Constraints:

• k $==$ lists.length

• $0 \leq$ k $\leq 10^3$

• $0 \leq$ lists[i].length $\le 500$ ...