Problem 2 Some of your friends have gotten into the burgeoning eld of timeseries data mining, in which one looks for patterns in sequences of events that occur over time. Purchases at stock exchanges, whats being bought, are one source of data with a natural ordering in time. Given a long sequence 8 of such events, your friends want an efcient way to detect certain \"patterns\" in them. For example, they may want to know if the four events buy Yahoo, buy eBay, buy Yahoo, buy Oracle occur in this sequence 3, in order but not necessarily consecutively