23. Merge k Sorted Lists

https://leetcode.com/problems/merge-k-sorted-lists/

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.

Example:

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

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Time - O(m * log k) - m = length of longest list
Space - O(k)
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Related problems
kth-largest-element-in-array
k-closest-points-to-origin