Ruby

1# Definition for singly-linked list.
2# class ListNode
3#     attr_accessor :val, :next
4#     def initialize(val = 0, _next = nil)
5#         @val = val
6#         @next = _next
7#     end
8# end
9# @param {ListNode[]} lists
10# @return {ListNode}
11def merge_k_lists(lists)
12  nodes = []
13  lists.each do |head|
14    while head
15      nodes << head.val
16      head = head.next
17    end
18  end 
19
20  return [] if nodes.empty?
21
22  nodes.sort!
23  new_list = ListNode.new(nodes[0])
24  curr = new_list
25  size = nodes.size
26  for i in 1...size 
27    curr.next = ListNode.new(nodes[i])
28    curr = curr.next
29  end
30
31  new_list
32end