Codeless question: Given a set of n items, which element occurs the largest number of times in the set? Bonus: How do you find out how many times some element k appears? — If the items are sorted, we can sweep from left to right and count them, since all identical items will be lumped together during sorting. To find out how often an arbitrary element k occurs, look up k using binary search in a sorted array of keys. Then use binary search in each direction to find where that run of the number begins and ends.