UNIVERSITY OF THE FREE STATE MAIN CAMPUS CSIS2614 DEPARTMENT: COMPUTER SCIENCE AND INFORMATICS CONTACT NUMBER:

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1 UNIVERSITY OF THE FREE STATE MAIN CAMPUS CSIS2614 DEPARTMENT: COMPUTER SCIENCE AND INFORMATICS CONTACT NUMBER: EXAMINATION: Additional Half Year Examination 2016 ASSESSORS: Prof. P.J. Blignaut MODERATOR: Dr. T. Beelders TIME: 4 hours MARKS: 100 (+ 3 bonus marks) 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 (Operator overloading) Develop a class that can be used to encapsulate operations with hexadecimal numbers. (1) 1.1 The class must have a private string field for the hexadecimal number. (1) 1.2 The constructor will assign a value to the private data field through a parameter. (2) 1.3 Override the ToString method to return the private data field. (2) 1.4 Provide a public method that will return the equivalent integer value. A hexadecimal number can be converted to its integer equivalent through the method Convert.ToInt32(string value, int frombase). (2) 1.5 Provide a static method to return the hexadecimal equivalent of an integer value. An integer can be converted to hex through the ToString("X") method. (2) 1.6 Provide a static operation for the hexadecimal + operator. (6) [16] You may test your class with the following Main() method: static void Main(string[] args) Hex Number1 = new Hex("2F"); Console.WriteLine(Number1 + "h = " + Number1.ToInt().ToString()); int inumber2 = 35; Console.WriteLine(iNumber2 + " = " + Hex.IntToHex(iNumber2) + "h"); Hex h1 = new Hex("F"); Hex h2 = new Hex("20"); Hex h3 = h1 + h2; Console.WriteLine(h1 + " + " + h2 + " = " + h3); Console.Write("Press any key to exit..."); Console.ReadKey(); 1

2 Question 2 (Delegates and events) Consider the partial implementation of a console application to display the area and perimeter of circles with varying radius. //2.1 Declare delegate... //2.2.1 Method to calculate the area of a circle with radius r private static... return Math.PI * r * r; //2.2.2 Method to calculate the perimeter of a circle with radius r private static... return 2 * Math.PI * r; //2.4 Method to write the property, radius and value of the specified property private static void Write(... Console.WriteLine(sCaption + "\t" + x.tostring() + "\t" + String.Format("0,6:F2", F(x))); static void Main(string[] args) //2.3 Instantiate instances of the delegate delfunction A =... delfunction P =... double[] radii = 2, 3, 2.3, 4.5, 6.7 ; Console.WriteLine("Property r Value"); Console.WriteLine("======== === ====="); foreach (double r in radii) Write("Area ", A, r); Write("Perimeter", P, r); Console.WriteLine(); Console.Write("Press any key to exit..."); Console.ReadLine(); //Main 2.1 Declare a delegate to define the signature of a method that will take a double parameter and return a double value. (3) 2.2 Complete the headers of the two methods to calculate the area and perimeter of a circle, given the radius as parameter. (4) 2.3 Complete the code to instantiate two instances of the delegate one to calculate the area of the circle and the other to calculate the perimeter. (4) 2.4 Complete the signature of the Write method. (3) [14] 2

3 Question 3 (Lists, Stacks and Queues) Consider the following partial implementation of a linked stack data structure. public interface IContainer<T> void MakeEmpty(); bool IsEmpty(); int Size(); public interface IStack<T> : IContainer<T> void Push(T data); void Pop(); T Top(); class CStack<T> : IStack<T> //Internal class private class Node public T Data get; set; public Node Next get; set; public Node(T data) Data = data; //class Node // Fields private Node top; private int numberelements; //Implementation of method in IContainer public void MakeEmpty() top = null; //Implementation of method in IContainer public int Size() return numberelements; //Implementation of method in IContainer public bool IsEmpty() return numberelements == 0; //3.1 Implementation of method in IStack //3.2 Implementation of method in IStack //3.3 Implementation of method in IStack // class LinkedStack<T> 3

4 Complete the code for the 3.1 Push() (8) 3.2 Pop() and (8) 3.3 Top() methods. (6) [22] Test your program with the following Main() method: static void Main(string[] args) CStack<int> Stack = new CStack<int>(); Console.WriteLine("Pushing..."); for (int i = 0; i < 10; i++) Console.WriteLine(i.ToString()); Stack.Push(i); Console.WriteLine(""); Console.WriteLine("Popping..."); for (int i = 0; i < 10; i++) Console.WriteLine(Stack.Top().ToString()); Stack.Pop(); Console.WriteLine(""); Console.Write("Press any key to exit..."); Console.ReadKey(); Question 4 (Regular expressions) Develop a console application to enable the user to enter any string and then extract the date of birth of a person. The date of birth will be in the format dd MMMM yyyy as in: Long ago, on Sunday 31 July 1960, my mother had a boy. Use the following regular expression: \d1,2\s(january February March April May June July August September October November December)\s\d4 [8] Question 5 (Trees and Graphs) Consider the scenario of a security guard who has to patrol the university campus at nights. He has to visit specific points at regular intervals. You will be provided with a partial solution that includes the main method and a generic graph class. The point-to-point distances between the various inspection points are defined in the main method of the program as vertices with edges of specific weight. Complete the program to print all possible patrol routes that start at the control room and visit all inspection points. It is not necessary that the routes end at the control room again. The program should also identify the shortest possible patrol route. The last part of the expected output is shown below. [28] CSIS2614 Additional Half Year Examination 2016

5 5 Question 6 (Dictionaries and Hash tables) A user complained that built-in trigonometric functions in the Math class in.net are too slow for his purposes. A solution was then proposed that a large number of (angle, function value) pairs should be loaded beforehand into a dictionary so that the values are immediately available on request. An incomplete solution is provided that should allow the user to select a trigonometric function (sin, cos or tan) along with an angle in degrees. The program should then evaluate the selected function for the given angle. Complete the class Trig as indicated. [15]

6 6 MEMORANDUM Question 1 (16) class Hex private string Value; public Hex(string value) Value = value; public override string ToString() return Value; public int ToInt() return Convert.ToInt32(Value, 16); public static Hex IntToHex(int i) Hex h = new Hex(i.ToString("X")); return h; public static Hex operator +(Hex h1, Hex h2) int i = h1.toint() + h2.toint(); return IntToHex(i); //class

7 7 Question 2 (14) class Program 2.1 public delegate double delfunction(double r ); private static double Area(double r ) return Math.PI * r * r; private static double Perimeter(double r ) return 2 * Math.PI * r; 2.4 private static void Write(string scaption, delfunction F, double r ) Console.WriteLine(sCaption + "\t" + r.tostring() + "\t" + String.Format("0,6:F2", F(x))); static void Main(string[] args) 2.3 delfunction A = new delfunction(area); delfunction P = new delfunction(perimeter); double[] radii = 2, 3, 2.3, 4.5, 6.7 ; Console.WriteLine("Property r Value"); Console.WriteLine("======== === ====="); foreach (double r in radii) Write("Area ", A, r); Write("Perimeter", P, r); Console.WriteLine(); Console.Write("Press any key to exit..."); Console.ReadLine();

8 8 Question 3 (22) 3.1 public void Push(T data) Node newnode = new Node(data); newnode.next = top; top = newnode; numberelements++; 3.2 public void Pop() if (IsEmpty()) throw new InvalidOperationException("Cannot pop empty stack."); else Node oldnode = top; top = top.next; numberelements--; oldnode = null; //Pop 3.3 public T Top() if (IsEmpty()) throw new InvalidOperationException("Cannot access top of stack."); else return top.data; Question 4 (8) class Program static void Main(string[] args) string s = "Long ago, on Sunday 31 July 1960, my mother had a boy."; string re February March April May June July August" + " September October November December)\s\d4"; Regex reg = new Regex(re); Match match = reg.match(s); if (match.success) Console.WriteLine("DOB: " + s.substring(match.index, match.length)); Console.Write("Press any key to exit..."); Console.ReadKey(); //Main //class Program

9 9 Question 5 (28) private void GetPaths(string start, string u, string Path, int weight) foreach (Edge edge in lstedges.where(edge => edge.u == u &&!Path.Contains("'" + edge.v + "'") && edge.v!= start )) GetPaths(start, edge.v, Path + "'" + edge.v + "', ", weight + edge.w); lstpaths.add(path + "'" + edge.v + "'"); lstweights.add(weight + edge.w); //GetPaths private static void ShortestPatrol() List<string> lstpaths; List<int> lstweights; string shortestpath = ""; int minlength = int.maxvalue; graph.getpaths("cr", out lstpaths, out lstweights); for (int i = 0; i < lstpaths.count; i++) string[] paths = lstpaths[i].split(new char[] ',', ' ', StringSplitOptions.RemoveEmptyEntries); if (paths.length == graph.size-1) Console.WriteLine((i + 1).ToString().PadLeft(3) + ": " + lstpaths[i] + " (" + lstweights[i] + ")"); if (lstweights[i] < minlength) minlength = lstweights[i]; shortestpath = (i + 1).ToString().PadLeft(3) + ": " + lstpaths[i] + " (" + lstweights[i] + ")"; //for Console.WriteLine("Shortest patrol route: " + shortestpath); //ShortestPatrol

10 10 Question 6 (15) class Trig private static Dictionary<decimal, double> diccos, dicsin, dictan; public static void Prepare() diccos = new Dictionary<decimal, double>(); dicsin = new Dictionary<decimal, double>(); dictan = new Dictionary<decimal, double>(); for (decimal deg = -180; deg < 180; deg += 0.01m) double rad = (double)deg * Math.PI / 180; diccos[deg] = Math.Cos(rad); dicsin[deg] = Math.Sin(rad); dictan[deg] = Math.Tan(rad); //Prepare public static double Cos(decimal degrees) degrees = (int)(degrees * 100) / 100m; if (diccos.containskey(degrees)) return diccos[degrees]; else return 0; //Cos public static double Sin(decimal degrees) degrees = (int)(degrees * 100) / 100m; if (dicsin.containskey(degrees)) return dicsin[degrees]; else return 0; //Sin public static double Tan(decimal degrees) degrees = (int)(degrees * 100) / 100m; if (dictan.containskey(degrees)) return dictan[degrees]; else return 0; //Tan //class