Merge Multiple Sorted Linked Lists

Problem Statement

Given several sorted linked lists, combine all of them into one sorted linked list and return the merged list. Consider the efficiency of your solution.

Examples

Input:
[
  2->5->7,
  2->4->6,
  3->8
]
Output: 2->2->3->4->5->6->7->8
  

Input:
[
  1->3->4,
  1->2->5,
  4->6
]
Output: 1->1->2->3->4->4->5->6
  

Constraints

• The number of linked lists will be between 1 and 25.
• Each linked list will contain between 0 and 600 nodes.
• Values of nodes are in the range -10,000 to 10,000.