Sort a linked list in O(n log n) time using constant space complexity.
Pascal's Triangle
Given an array of strings, return all groups of strings that are
anagrams.
Merge and Insert intervals
Given an array where elements are sorted in ascending order, convert it
to a height balanced BST.
Convert Sorted List to Binary Search Tree
A linked list is given such that each node contains an additional random
pointer which could point to any node in the list or null.

Return a deep copy of the list.
Binary Search Tree
sortList: Sort a linked list in O(n log n) time using constant space
complexity.