[Categorisation] Incorrect categorisation of merged k sorted lists

[caramelmelmel]

The following problem: https://leetcode.com/problems/merge-k-sorted-lists/solutions/ is a linkedList problem instead of an array problem. The data structure presented as an input is a LinkedList as a particular node cannot be accessed directly via an index value that is O(1) in time. Hence, this should be a LinkedList problem.