Write a function that accepts an array of k linked lists as input, where the nodes in each list are arranged in ascending order.
Your task is to merge all the input lists into a single linked list, ensuring that all nodes remain in sorted ascending order, and return this combined result.
Constraints:
Examples:
// Example 1:
const lists1 = [createList([1, 2, 4]), createList([1, 3, 5]), createList([3, 6])];
console.log(mergeKLists(lists1));
// Output: [1, 1, 2, 3, 3, 4, 5, 6]
// Example 2:
const lists2: ListNode[] = [];
console.log(mergeKLists(lists2));
// Output: null
// Example 3:
const lists3 = [createList([])];
console.log(mergeKLists(lists3));
// Output: null