Hackerrank test: 1) Print Roman number equivalent for numbers 1-1000 2) Order a list of words appearing in a file by number of letters but maintain original order ("stable sorting") of words with same length 3) Implement a stack class with methods to do some specific operations mentioned in the question. Phone/Codepad interview: 1) Given a series of prices, find the one buy/sell trade pair which gives the maximum profit 2) Modification of 1. For the same prices, find the maximum profit possible with any number of buy/sell allowed (at each step/price, you can buy, sell or do nothing, no short sell allowed)