1) An online retailer is releasing a new feature called "What are my friends buying?". The feature lists a set of products that you have not already purchased from the things that your friends have bought, in order of most bought to least bought. To help with this, we have the following 2 APIs. Complete the function that takes in a person and returns the items that the person's friends are buying. 2) Instead of your friends, what about your social circle? A social circle of a person is defined as the person's friends and their friends.

Given a list of words, match all words with other words from the list that are a prefix for the word.

Given a list of lists in a lexigraphic ordering, return the ordering of the characters in the language.

1) Return a list of all the paths to leaves in the tree. 2) Given a lexicographically sorted list of words, return the order of the alphabet.

Print a linked list in reverse.

Given a linked list with an additional pointer referring to another node in the list, return a deep copy of the list.

1) Find the K nearest points to a vertex. 2) Change your solution under the condition that you have an input file of size 500 Petabytes.

1) Write a square root function. 2) Find the K closest points

1) Write a function to determine the coin closest to you from a list of positions using Manhattan Distance 2) Find the cutoff at which to switch over to a breadth first search algorithm 3) Determine which is the optimal coin to collect when there are opponents present (each opponent only collects one coin)

Given a non-empty array of integers, return the k most frequent elements

1) Write a function to reverse a given string 2) Given an unsorted array of unique integers (size n + 1) and a second array that is identical to the first array but missing one integer (size n), find and output the missing integer