QUEEN MARY, UNIVERSITY OF LONDON

Transcription

1 QUEEN MARY, UNIVERSITY OF LONDON BSC IN THE FACULTY OF ENGINEERING AND MATHEMATICAL SCIENCES Examination No.: UserId. MODULE: DCS100: PROCEDURAL PROGRAMMING 2004 MOCK TEST 2 Time allowed: 2 hours (120 minutes). Answer ALL FOUR (multi-part) questions There are four questions on this examination paper. Marks for each question part are indicated below each question part and total marks per question are shown at the end of each question. Each question is worth 25 marks, so the whole examination is marked out of 100 marks. This is scaled to 50 marks out of 100 (50%) of the final module total Answer the questions in accordance with the instructions given with each question [Should your answer not fit in the space provided, you may continue on the reverse of the page and in a supplementary answer book provided that you record your examination number only and indicate clearly the question number and part to which your answer relates]. Page 1 of 12

2 Question 1 [25 marks] a) Explain what is meant by: i) An assignment statement. ii) An if statement. b) Write single lines of Java code that do each of the following: i) Declare and initialise to 12 an integer variable called noon. [1 Mark] Question 1 continues overleaf. Page 2 of 12

3 Question 1 continued. ii) Declare an array of Strings called today to hold 24 Strings [2 Marks] iii) Store in array today at index position 8 the word breakfast. [2 Marks] iv) Store in array today at position given by the variable noon the word lunch. v) Print to the screen the word stored in array today at position given by variable noon. [2 Marks] [2 Mark] [Total marks for part 1b:9 Marks] c) Write a Java program using Brinch Hansen's input-output facilities that repeatedly asks the user to type in two numbers and prints out the largest of the two. After each pair is processed the program should ask the user if they want to continue. [10 Marks] [Total Marks for Question 1: 25] Page 3 of 12

4 Question 2 [25 marks] a) For each of the following code fragments state how many times the word "Yes!" will be printed justifying your answers. i) int i=1; while(i <= 10) out.writeln("yes!"); i = i+1; Justification: ii) int i=20; while(i < 20) out.writeln("yes!"); i = i+1; Justification: [2 Marks] iii) int i=20; while(i!= 0) out.writeln("yes!"); i = i-1; Justification: [2 Marks] Question 2 continues overleaf. [2 Marks] Page 4 of 12

5 Question 2 continued. iv) int i = 5; while(i > 0) out.writeln("yes!"); i = i+1; Justification: b) Compare and Contrast loops within loops and loops in sequence [Total Marks for Part 2a: 9] Question 2 continues overleaf. [6 Marks] Page 5 of 12

6 Question 2 continued. c) Write a Java program which inputs 2 positive integers, n and m, from the user and outputs an n by m line rectangle of numbers where printed on each line is a count from 1 to n. For example, if 5 and 3 are input the output should be: If 2 and 4 input the output should be: [10 Marks] [Total Marks for Question 2: 25] Page 6 of 12

7 Question 3 [25 marks] a) Explain what the following method does: public static boolean binary(int[] a, int target, int low, int high) boolean FOUND = true; boolean NOT_FOUND = false; if ((low == high) & (a[low] == target)) return FOUND; if ((low == high) & (a[low]!= target)) return NOT_FOUND; int mid = (low + high)/2; if (target <= a[mid]) return binary(a, target, low, mid); else return binary(a, target, mid+1, high); Question 3 continues overleaf. [9 Marks] Page 7 of 12

8 Question 3 continued. b) Compare and Contrast linear search and binary search. Question 3 continues overleaf. [6 Marks] Page 8 of 12

9 Question 3 continued. c) Write a Java program that inputs a series of 100 names from a file, storing them in an array. The program should then ask the user for a name to search for and perform a linear search to find it from the array, printing the position of the first place it appears. [10 Marks] [Total Marks for Question 3: 25] Page 9 of 12

10 Question 4 [25 marks] a) Explain the following terms illustrating your answers with examples. i) "recursive method" ii) "recursive call" iii) "divide and conquer" Question 4 continues overleaf. [Total marks for part 4a:9 Marks] Page 10 of 12

11 Question 4 continued. b) Trace the execution of the following recursive method, f, working out what is printed when called as follows: public static int f (int n) if (n == 0) return 1; else if (n == 1) return 0; else return (n * f(n-2)); i) int a = f(6); out.writeln( a ); ii) int a = f(7); out.writeln( a ); Question 4 continues overleaf. Page 11 of 12

12 Question 4 continued. c) Write a Java method that is equivalent to the following method but that uses recursion rather than a while loop. public static int f (int n) boolean finished = false; int result = 0; while (! finished) if (n==0) result = result + 3; finished = true; else result = result + n; n = n-1; return result; [10 Marks] [Total Marks for Question 4: 25] END OF EXAMINATION Page 12 of 12