UNIVERSITY OF THE FREE STATE DEPARTMENT OF COMPUTER SCIENCE AND INFORMATICS CSIS 2614 MODULE TEST 2

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1 UNIVERSITY OF THE FREE STATE DEPARTMENT OF COMPUTER SCIENCE AND INFORMATICS CSIS 2614 MODULE TEST 2 DATE: 13 May 2016 TIME: 3.5 hours MARKS: 112 ASSESSOR: Prof. P.J. Blignaut BONUS MARKS: 5 MODERATOR: Dr T. Beelders This is an open-book test. You may use ONLY the text book by Nakov. No other sources are allowed. Internet access will not be available for the duration of the assessment. You may use the tools available in Visual Studio such as IntelliSense. No mobile computing devices may be active for the duration of the assessment (Mobile phones, tablets, etc). Question 1 (Lists, Stacks & Queues) 1.1 Consider the simple linked list implementation as provided in the file LinkedList.cs. Consider also its usage in the Main() method below. //Create list LinkedList<string> lststrings = new LinkedList<string>(); //Add elements one at a time lststrings.add("john"); lststrings.add("susan"); lststrings.add("abel"); lststrings.add("ben"); //Print elements for (int i = 0; i < lststrings.count; i++) Console.Write(lstStrings[i] + ", "); //Change the name of the first entry lststrings[0] = "Bennie"; //Print elements again for (int i = 0; i < lststrings.count; i++) Console.Write(lstStrings[i] + ", "); //Opportunity to read output Console.Write("Press any key to exit..."); //Main Add an indexer to the class that can be used to print or change the value of one of the items. (12) 1

2 1.2 Using.Net queue, develop a console application to allow a user to enter a specific directory on his hard drive and then display a breadth first traversal of all subdirectories of the given directory. For example, for the directory structure on the left, the output should be as on the right: (15) [27] Question 2 (Strings and Regular expressions) Consider the following regular expression to validate a date in the format dd/mm/yyyy. Develop a console application that will keep on prompting a user until he has entered a valid date in this format. [9] (^((((0[1-9]) ([1-2][0-9]) (3[0-1])) ([1-9]))\x2F(((0[1-9]) (1[0-2])) ([1-9]))\x2F(([0-9]2) (((19) ([2]([0]1)))([0-9]2))))$) Question 3 (Trees and Graphs) 3.1 Consider the partial class for a binary search tree (BST) that will be provided to you. Also consider the Main() method below. //Create tree BST tree = new BST(); tree.insert(5); tree.insert(8); tree.insert(4); tree.insert(6); tree.insert(3); tree.insert(9); tree.insert(7); tree.insert(8); tree.insert(9); tree.insert(3); tree.insert(6); tree.insert(2); tree.insert(5); tree.insert(1); tree.insert(8); tree.insert(5); tree.insert(9); //Number of leaves Console.WriteLine("Number of leaves: " + tree.leaves); //Opportunity to read output Console.Write("Press any key to exit... "); //Main Add a depth-first recursive procedure to the BST class to count the number of nodes and leaves. [15] 3.2 A console application will be provided that uses a list of edges to represent a road map of the Free State province. Add a public method, ListRoutes, to list all the routes from a given starting point to a given end point. This method may call another method which, in turn, will call itself recursively. [26] 2

3 Question 4 (Dictionaries and Hash tables) 4.1 The file, Thesaurus.txt contains thousands of records of English words with semantically nearly equivalent alternatives. Every record is terminated with a line end character. Words within a record are comma-separated. Enter the records into.net dictionary with the first word being the key and the entire record being the value. Allow the user to enter a word and display the list of synonyms for that word. The user must be able to enter one word after the other until he/she wants to terminate the program. (26) 4.2 Consider the incomplete program in the file AfrikaansEnglish.cs. The program makes use of a hash table implemented as an array of arrays. The outer array constitutes the hash table and is indexed by hash code. The inner array handles collisions by chaining. Write the method AddEntries(). (14) [40] 3

4 MEMORANDUM Question 1.1 (12) public T this [int index] get Node current = head; for (int i = 0; i < index; i++) current = current.next; return current.element; set Node current = head; for (int i = 0; i < index; i++) current = current.next; current.element = value; Question 1.2 (15) Console.Write("\tStarting directory: "); string rootdir = Console.ReadLine(); DirectoryInfo dir = new DirectoryInfo(rootDir); TraverseDirBreadthFirst(dir); Console.Write("\tPress any key to exit..."); //Main private static void TraverseDirBreadthFirst (DirectoryInfo dir ) Queue<DirectoryInfo> qvisited = new Queue<DirectoryInfo>(); qvisited.enqueue(dir); while (qvisited.count > 0) DirectoryInfo currentdir = qvisited.dequeue(); Console.WriteLine("\t" + currentdir.fullname); DirectoryInfo[] children = currentdir.getdirectories(); foreach (DirectoryInfo child in children) qvisited.enqueue(child); //while //TraverseDirBF 4

5 Question 2 (9) string sinput = ""; bool isvalid = false; do Console.Write("Date (dd/mm/yyyy): "); sinput = Console.ReadLine(); string re ([1-2][0-9]) (3[0-1])) ([1-9]))\x2F(((0[1-9]) (1[0-2])) ([1-9]))\x2F(([0-9]2) (((19) ([2]([0]1)))([0-9]2))))$)"; isvalid = Regex.Match(sInput, re).success; while (!isvalid); Console.WriteLine(sInput); Console.Write("Press any key to exit..."); Question 3.1 (15) private int nleaves; public int Leaves get nleaves = 0; VisitNodesDFS(Root); return nleaves; private void VisitNodesDFS(Node node) if (node!= null) VisitNodesDFS(node.Left); if (node.left == null && node.right == null) nleaves++; VisitNodesDFS(node.Right); 5

6 Question 3.2 (26) private List<string> lstroutes; private List<int> lstdistances; private List<int> lsttimes; public void ListRoutes(string Origin, string Destination, out List<string> lstroutes, out List<int> lstdistances, out List<int> lsttimes) this.lstroutes = new List<string>(); this.lstdistances = new List<int>(); this.lsttimes = new List<int>(); ListRoutes(Origin, Destination, Origin, "", 0, 0); lstroutes = this.lstroutes; lstdistances = this.lstdistances; lsttimes = this.lsttimes; //ListRoutes private void ListRoutes(string Origin, string Destination, string Start, string Route, int Distance, int Time) foreach (Edge route in lstalledges.where(edge => edge.start == Start &&!Route.Contains(Origin) &&!Route.Contains(edge.End))) ListRoutes(Origin, Destination, route.end, Route + route.end + " ", Distance + route.distance, Time + route.time); if (route.end == Destination) lstroutes.add(route + route.end + " "); lstdistances.add(distance + route.distance); lsttimes.add(time + route.time); //ListRoutes 6

7 Question 4.1 (26) StreamReader rdr = new StreamReader("Thesaurus.txt"); string sthesaurus = rdr.readtoend(); rdr.close(); string[] entries = sthesaurus.split('\n'); Dictionary<string,string> dic = new Dictionary<string,string>(); foreach (string entry in entries) string skey = entry.split(',')[0]; if (!dic.containskey(skey)) dic.add(skey, entry); Console.WriteLine("Number of entries : " + dic.count); string sword = ""; do Console.Clear(); Console.Write("Word ('XXX' to exit): "); sword = Console.ReadLine(); if (dic.containskey(sword)) Console.Write(dic[sWord]); else if (sword.toupper()!= "XXX") Console.Write("No such entry."); while (sword.toupper()!= "XXX"); //Main Question 4.2 (14) private static void AddEntries(Entry[][] Entries ) StreamReader f = new StreamReader("Dictionary.txt"); while (!f.endofstream) string s = f.readline() + "\t"; string skey = s.split('\t')[0], svalue = s.split('\t')[1]; int hashcode = GetHashCode(sKey, Entries.Length); int k = Entries[hashCode].Length + 1; Array.Resize(ref Entries[hashCode], k); Entries[hashCode][k - 1] = new Entry(sKey, svalue); f.close(); //AddEntries 7