computer science homework

1 1 CPS 350: Assignment 3 Due 11:55 pm, Wednesday, 3/15/2017 ( 200 pts) This is a team project . At most two students are in one team No late submission will be accepted Receive 5 bonus points if turn in the complete work without errors at least one day before deadline Receive an F for this course if any academic dishonesty occurs 1. Purpose The purpose of this assignment is to implement sort ing algorithms for the autocomplete application. 2. Description Write a program to implement autocomplete for a given set of N terms , where a term is a query string and an associated nonnegative wei ght. That is, given a prefix, find all queries that start with the given prefix, in descen ding order of weight.

Autocomplete is pervasive in modern applications. A s the user types, the program predicts the complete query (typically a word or phrase) that the user intends to type.

Autocomplete is most effective when there are a lim ited number of likely queries. For example, the Internet Movie Database uses it to display the names of movies as the user types; search engines use it to display suggestions as the user enters w eb search queries; cell phones use it to speed up text input. In these examples, the application predicts how lik ely it is that the user is typing each query and presents to the user a list of the top-ma tching queries, in descending order of weight. These weights are determined by historic al data, such as box office revenue for movies, frequencies of search queries from othe r Google users, or the typing history of a cell phone user. For the purposes of t his assignment, you will have access to a set of all possible queries and associated wei ghts (and these queries and weights will not change). The performance of autocomplete functionality is cr itical in many systems. For example, consider a search engine which runs an aut ocomplete application on a server 2 2 farm. According to one study, the application has o nly about 50ms to return a list of suggestions for it to be useful to the user. Moreov er, in principle, it must perform this computation for every keystroke typed into the search bar and for every user !

In this assignment, you will implement autocomplete by sorting the terms by query string (with running time O(N log N) in sorting, or even better, where N is the of terms); binary searching to find all query strings that start with a given prefix (with running time O(log N)); and sorting the matching terms by weight (with running time O (M log M) in sorting, where M is the number of matching terms). Finally display results for the user. The following shows the top s even queries (city names) that start with AI M with weights equal to their populations.

2.1. Part 1: autocomplete term (60 pts) Write an immutable data type Term.java that represents an autocomplete term: a query string and an associated integer weight. You must i mplement the following API, which supports comparing terms by three different o rders: lexicographic order by query string (the natural order); in descending order by weight (an alternate order); and lexicographic order by query string but using o nly the first r characters (a family of alternate orderings). The last order may seem a bit odd, but you will use it in Part 3 to find all query strings that start with a given prefix (of length r).

public class Term implements Comparable { /* Initializes a term with the given query string a nd weight. */ public Term(String query, long weight) /* Compares the two terms in descending order by we ight. */ public static Comparator byReverseWeightOrder () /* Compares the two terms in lexicographic order bu t using only the first r characters of each query. */ public static Comparator byPrefixOrder(int r) /* Compares the two terms in lexicographic order by query. */ public int compareTo(Term that) 3 3 // Returns a string representation of this term in the following forma t: // weight (i.e., ??.toString()), followed by a tab, followed by query. public String toString() } Corner cases. The constructor should throw a java.lang.NullPointerException if query is null and a java.lang.IllegalArgumentException if weight is negative.

The byPrefixOrder() method should throw a java.lang.IllegalArgumentException if r is negative.

Performance requirements. The string comparison functions should take time proportional to the number of characters needed to resolve the comparison.

2.2. Part 2: binary search (30 pts) When binary searching a sorted array that contains more than one key equal to the search key, the client may want to know the index o f either the first or the last such key. Accordingly, implement the following API: public class BinarySearchDeluxe { /* Returns the index of the first key in a[] that e quals the search key, or -1 if no such key. */ public static int firstIndexOf(Key[] a, Key k ey, Comparator comparator) /* Returns the index of the last key in a[] that eq uals the search key, or -1 if no such key. */ public static int lastIndexOf(Key[] a, Key ke y, Comparator comparator) } Corner cases. Each static method should throw a java.lang.NullPointerException if any of its arguments is null . You should assume that the argument array is in s orted order (with respect to the supplied comparator). Performance requirements. The firstIndexOf() and lastIndexOf() methods should make at most 1 + ⌈log 2 N ⌉ compares in the worst case, where N is the length of the array. In this context, a compare is one call to comparator.compare() .

2.3. Part 3: autocomplete (70 pts) In this part, you will implement a data type that p rovides autocomplete functionality for a given set of string and weights, using Term and BinarySearchDeluxe . To do so, sort the terms in lexicographic order; use binary search to find the all query strings 4 4 that start with a given prefix; and sort the matching terms in descending order by weight. Organize your program by creating an data t ype Autocomplete with the following API: public class Autocomplete { // implement sorting a lgorithm in this class /* Initializes the data structure from the given ar ray of terms. */ public Autocomplete(Term[] terms) /* Returns all terms that start with the given pref ix, in descending order of weight. */ public Term[] allMatches(String prefix) } Corner cases. The constructor should throw a java.lang.NullPointerException if its argument is null or if any of the entries in its argument array are null . Each method should throw a java.lang.NullPointerException if its argument is null .

Performance requirements. The constructor should make proportional to N log N compares (or better) in the worst case, where N is the number of terms.

The allMatches() method should make proportional to log N + M log M compares (or better) in the worst case, where M is the number of matching terms. In this context, a compare is one call to any of the compare() or compareTo() methods defined in Term .

2.4. Input format for testing (30 pts) We provide a number of sample input files for testi ng. Each file consists of an integer N followed by N pairs of query strings and nonnegative weights. Th ere is one pair per line, with the weight and string separated by a tab. A weight can be any integer between 0 and 2^63 1. A query string can be an arbitrary sequence of Unicode characters, including spaces (but not newli nes). The file wiktionary.txt contains the 10,000 most common words in Project Gutenberg, with weights proportional to their frequ encies. The file cities.txt contains over 90,000 cities, with weights equal to their populations. % more wiktionary.txt 10000 5627187200 the 3395006400 of 2994418400 and 2595609600 to 1742063600 in 1176479700 i 1107331800 that 1007824500 was % more cities.txt 93827 14608512 Shanghai, China 13076300 Buenos Aires, Argentina 12691836 Mumbai, India 12294193 Mexico City, Distrito Federal, Mexic o 11624219 Karachi, Pakistan 11174257 İstanbul, Turkey 10927986 Delhi, India 10444527 Manila, Philippines 5 5 879975500 his ...

392323 calves 10381222 Moscow, Russia ...

2 Al Kh āniq, Yemen Below is a sample client that takes the name of an input file and an integer k as command-line arguments. It reads the data from the file; then it repeatedly reads autocomplete queries from standard input, and print s out the top k matching terms in descending order of weight.

public static void main(String[] args) { // read in the terms from a file String filename = args[0]; // first argument from command line In in = new In(filename); int N = in.readInt(); Term[] terms = new Term[N]; for (int i = 0; i < N; i++) { long weight = in.readLong(); // read the next weight in.readChar(); // scan past the tab String query = in.readLine(); // read the next query terms[i] = new Term(query, weight); // construct the term } // read in queries from standard input and print th e top k matching terms int k = Integer.parseInt( args[1]); // 2 nd argument from command line Autocomplete autocomplete = new Autocomplete(te rms); while ( StdIn.hasNextLine()) { String prefix = StdIn.readLine(); Term[] results = autocomplete.allMatches(pr efix); for (int i = 0; i < Math.min(k, results.len gth); i++) System.out.println(results[i]); } } Here are a few sample executions:

% java Autocomplete wiktionary.txt 5 auto 619695 automobile 424997 automatic comp 13315900 company 7803980 complete 6038490 companion 5205030 completely 4481770 comply the 5627187200 the 334039800 they 282026500 their 250991700 them 196120000 there % java Autocomplete cities.txt 7 M 12691836 Mumbai, India 12294193 Mexico City, Distrito Federal, Mexico 10444527 Manila, Philippines 10381222 Moscow, Russia 3730206 Melbourne, Victoria, Australia 3268513 Montréal, Quebec, Canada 3255944 Madrid, Spain Al M 431052 Al Ma ḩallah al Kubrá, Egypt 420195 Al Man şūrah, Egypt 290802 Al Mubarraz, Saudi Arabia 258132 Al Mukall ā, Yemen 227150 Al Miny ā, Egypt 128297 Al Man āqil, Sudan 99357 Al Ma ţar īyah, Egypt first argument 2nd argument defined in In.java , to read data from files and URLs defined in StdIn.java, to read data from keyboard 6 6 Interactive GUI (optional, but fun and no extra wor k):

Compile AutocompleteGUI.java . The program takes the name of a file and an integer k as command-line arguments and provides a GUI for t he user to enter queries.

It presents the top k matching terms in real time. When the user selects a term, the GUI opens up the results from a Google search for t hat term in a browser. % java AutocompleteGUI cities.txt 7 3. If your program does not compile, you receive zero points for that program. Additional deductions: 1. (5 points) Your code does not follow the style guid e discussed in class/textbook.

2. (30 points) Your code does not have author name, da te, purpose of this program, comments on the variables and methods, etc. 4. One submission for a team . Zip/submit your entire project , including Autocomplete.java , BinarySearchDeluxe.java , and Term.java . You may NOT call any library functions other than those in java.lang and java.util . Finally, submit a report file (10 points) and answer the following questions:

a) Known bugs limitations of this assignment.

b) Describe any serious problems you encountered. c) List any other comments here. Feel free to provide any feedback on how much you learned from doing the assignment, and whether you enjoyed doing it.