Bloomberg interview question

For a system design interview round, I got a task to design a digest collection and notification system. In a nutshell, data is digested from multiple sources and users are notified at configured intervals about recent events. The coding interview rounds had the following problems: - A candy crush-like problem - Count the number of islands - Given a number of exchange operating hours, determine whether a trade with the specified start and end time could be performed - Design a response buffering class