Given a sequence of items (consider them votes for candidates), return the candidate with the majority of the votes. ("Majority" means more than half; that is stronger than "plurality," which means more than anyone else.) If no item has a majority, return None. Now you can solve the problem by going through the sequence once, keeping a running total for each candidate. That will solve the problem, but it requires storing a count for each candidate. There is a trickier way to do it so that, even if there are hundreds of candidates and million of votes, you only need to store one intermediate count, and one candidate at a time. (You don't need to find the tricky way to answer this question, but think about it and see if you can.)