I was asked to answer three computer science questions: 1. find the most frequent item in an array. 2. given a string and an int, return the longest sub string which length is less than n and the sub string does not contain partial parts from words in the argument string. 3. provide data structure which support the next methods: - init(n) -- O(n) - set(key, value) -- O(1) - get(key) -- O(1) - reset() -- O(1)