Design a search autocomplete system for a search engine. Users may input a sentence (at least one word and end with a special character '#'). You are given a string array sentences and an integer array times both of length n where sentences[i] is a previously typed sentence and times[i] is the corresponding number of times the sentence was typed. For each input character except '#', return the top 3 historical hot sentences that have the same prefix as the part of the sentence already typed. Here are the specific rules: The hot degree for a sentence is defined as the number of times a user typed the exactly same sentence before. The returned top 3 hot sentences should be sorted by hot degree (The first is the hottest one).