2009 Academic Challenge

Transcription

1 2009 Academic Challenge COMPUTER SCIENCE TEST - STATE FINALS This Test Consists of 30 Questions Computer Science Test Production Team Jim Feher, McKendree College Author/Team Leader Barry Bookout, East Central College Author Scott Elliott, John A. Logan College Reviewer Mary Weaver, WYSE Coordinator of Test Production GENERAL DIRECTIONS Please read the following instructions carefully. This is a timed test; any instructions from the test supervisor should be followed promptly. The test supervisor will give instructions for filling in any necessary information on the answer sheet. Most Academic Challenge sites will ask you to indicate your answer to each question by marking an oval that corresponds to the correct answer for that question. Only one oval should be marked to answer each question. Multiple ovals will automatically be graded as an incorrect answer. If you wish to change an answer, erase your first mark completely before marking your new choice. You are advised to use your time effectively and to work as rapidly as you can without losing accuracy. Do not waste your time on questions that seem too difficult for you. Go on to the other questions, and then come back to the difficult ones later if time remains. *** TIME: 40 MINUTES *** DO NOT OPEN TEST BOOKLET UNTIL YOU ARE TOLD TO DO SO! 2009 Worldwide Youth in Science and Engineering WYSE, Worldwide Youth in Science and Engineering and the WYSE Design are service marks of and this work is the Copyright 2009 of the Board of Trustees of the University of Illinois at Urbana - Champaign. All rights reserved.

2 WYSE Academic Challenge Computer Science Test (State Finals) A SATA (Serial Advanced Technology Attachment) hard drive spins its platters at a rate of 4800 rotations per minute. The transfer rate of data from the drive is 1.5 Megabits per second and the CPU has a clock rate of 3 GHz. Using this information, determine the best estimate for the maximum seek time to find a file of size 500Kilobits on the hard drive. a) 1/3 sec b) 1/80 sec c) 1/600 sec d) 1/4800 sec e) 1/(1,500,000) sec 2. Peer to Peer (P2P) applications such as LimeWire, emule, or BitTorrent have all of the following advantages except: a) that they are distributed, which prevents them from being blocked at one source. b) that they exchange data from multiple sources which allows for faster data exchange. c) that they allow users to legally download any copyrighted material. d) P2P applications have all of the advantages listed in a-c. e) P2P applications have none of the advantages listed in a-c. 3. Which set of transitions from the two-bit binary state 00 represents a Gray code? a) b) c) d) both a and b e) none of the above 4. All are true regarding the Java Virtual Machine (JVM) except which of the following? a) Running programs on the JVM can be slower than those run directly on the CPU. b) The JVM is a simulated machine allowing java programs to run on any system that implements the JVM. c) The clock speed of the JVM is dependent on the distances between the circuits that contain the transistors of the JVM. d) The JVM runs compiled byte code of java programs. e) Both (a) and (b) are true. 5. What is the result in decimal (base 10) of subtracting the 8-bit, two's complement number from the 8-bit, two's complement number ? a) -74 b) 74 c) -75 d) 75 e) overflow 6. What is the equivalent Boolean expression for this circuit if A is TRUE and B is FALSE? a) TRUE b) FALSE c) C d) NOT C e) none of the above

3 Computer Science 2 7. Use the Karnaugh Map listed below to determine the minimal sum of products logical function that corresponds to the table. A'B' A B AB AB C D T T F F C D T T T T CD T T T T CD F F F F a) not A or D b) (not A and not C) or (C and D) c) (not A and not B and not C) or D d) (not A and not C) or D e) (not C and D) or (C and D) or (not A and not C) 8. Given a zero operand instruction set using a stack architecture, which of the expressions given is the result of evaluating the instructions provided? The stack operands are as follows: ADD - Pops top two items from stack, adds them, pushes the result on top SUB - Subtracts top item from next item on stack, leaves only the result on top MUL - Pops top two items from stack, multiplies them, pushes result on top PUSH - put item on top of stack POP - take item off top of stack PUSH A PUSH B MUL PUSH A PUSH C PUSH D MUL SUB ADD POP X a) X = (A * B) * D C + A b) X = (A * B) + (D * C A) c) X = (A * B) (D C * A) d) X = (A * B) - (D * C) + A e) X = (A * B) + (A C * D) 9. Which of the following, if any, is NOT true regarding binary search algorithms? a) Items must already be sorted to use a binary search. b) Linked structures using pointers can be searched with such an algorithm. c) Binary searches are much faster than linear searches. d) The approximate runtime of a binary search of a list of n items is O(log 2 n). e) All of the above statements are true.

4 Computer Science For a list of n items, algorithm 1 has an execution time of O(2n 2 + 5), algorithm 2 has an execution time of O(n 2 ) and algorithm 3 has an execution time of O(n 2 /3 n). Which of the following is true regarding the three algorithms? a) The execution time in order of decreasing time to compute is 1, 2, 3. b) The execution time in order of decreasing time to compute is 3, 2, 1. c) The execution times are equivalent. d) All of the algorithms must be for sorting algorithms. e) All of the algorithms must employ at least one for, while or do/while loop. 11. Which of the following is true regarding the bubble sort and quick sort algorithm? a) The average execution time of quick sort is slower than the bubble sort. b) Both of the sorts have a worst case execution time of O(n 2 ) for n items. c) Both of the sorts have an average execution time of O(n log(n) ) for n items. d) Both sorts must sort items in increasing order. e) None of the above are true. 12. What is the value of sum at the end of the following code? struct list { int data; list *next; ; // list *b, *head; already declared with head pointing to list int sum = 0; for (b=head; b->next!= NULL; b=b->next) { sum += b->data; a) -2 b) 4 c) 7 d) 9 e) Which of the following is true regarding list or linked list and array data structures? a) Both lists and arrays are random access structures. b) Both lists and arrays can dynamically increase the number of items they contain. c) Both lists and arrays can be sorted. d) None of the above statements are true. e) All of the above statements are true. 14. A hash table data structure has which of the following properties? a) Items stored in the hash table are sorted. b) Items are accessed through an index computed by a function applied to the value. c) All items are chained together much like linked lists. d) The hash table has the same structure as a tree. e) Hash tables have none of the properties mentioned above.

5 Computer Science A depth-first search is conducted for the following graph, starting at node M. In the case that more than one option for the next direction to search is available at a node, it will chose the node of lower value. In what order are the nodes visited? a) M G D H A L S P V b) M G S D H P V A L c) M G S D A H L P V d) M S G V P H D L A e) M G D A H L S P V //*** Code segment for problems 16, 17 and 18 ***// float dist(int p[][2], int i, int j) { int dx = p[i][0] - p[j][0]; int dy = p[i][1] - p[j][1]; return pow(dx*dx + dy*dy, 0.5); // initialization of array in main int p[][2] = {{1, 1, {3, 4, {6, 5, {7, 8; 16. Which is numerically equivalent to the return value of the call dist(p,3,1)? a) sqrt(32) b) sqrt(41) c) sqrt(18) d) sqrt(3) e) sqrt(34) 17. Given the above initialization of p, what is printed when the following code executes? for (int i=0; i < 3; i++) for (int j=0; j < 2; j++) cout << p[i][j] << ; a) b) c) d) e) Given the above initialization of p, what is printed when the following code executes? for (int i=0; i < 2; i++) for (int j=0; j < 3; j++) cout << p[i][j] << ; a) b) c) d) e) //*** Code segment for questions 19, 20 and 21 ***// int a = 11, b = 7, c = 3; do { a += 2; b--; if (a % b - c < 0) cout << a%b-c << ; while (a/b/c <= 1); cout << a/b/c;

6 19. How many times does the do-while loop execute? Computer Science 5 a) 1 b) 2 c) 3 d) 4 e) What is printed by the do-while loop? a) b) c) -2 d) -3 e) nothing 21. What is printed by the cout << a/b/c; statement? a) 0 b) 1 c) 2 d) 3 e) none of the above //*** Code segment for problems 22, 23, 24 and 25 ***// #define SIZE 5 void array_splice (int A[], int i1, int i2) { int step = i2 - i1; for (int i=0; i < SIZE; i++) { (i >= i1) && (A[i] = (i+step < SIZE)? A[i+step] : 0); cout << A[i] << ; 22. What is printed by the following function call? int num_list[] = {2, 4, 3, 5, 1; array_splice(num_list, 2, 3); a) b) c) d) e) none of the above 23. What is printed by the following function call? int num_list[] = {2, 4, 3, 5, 1; array_splice(num_list, 3, 2); a) b) c) d) e) none of the above 24. Assume that the function definition were changed to make the array A const. This change would result in changing this line from: void array_splice (int A[], int i1, int i2) { to: void array_splice (const int A[], int i1, int i2) { Which of the following would result? a) The output statement would always display the same number. b) The array A would never be changed. c) The program would result in a run time error. d) The program would not compile. e) The index would always be out of the legal bounds of the size of the array.

7 25. Which of the following is not represented in this line of code? Computer Science 6 (i >= i1) && (A[i] = (i+step < SIZE)? A[i+step] : 0 ); a) tertiary operator b) boolean operator c) short-circuit condition d) unary operator e) binary operator //*** NOTE: Code for classes, Rectangle and Square ***// //*** are used for questions ***// class Rectangle { private: float width, height; public: Rectangle(float=1.0, float=1.0); void SetWidth(float); float GetWidth() const {return width; void SetHeight(float); float GetHeight() const {return height; float GetArea() const {return height*width; float GetPerimeter()const {return 2*height+2*width; ~Rectangle(); ; Rectangle::Rectangle(float w, float l) { SetWidth(w); SetHeight(l); cout << "." << endl; void Rectangle::SetWidth(float w) { width = (w>0)? w : 1; void Rectangle::SetHeight(float h){ height = (h>0)? h : 1; Rectangle::~Rectangle() { cout << "." << endl; class Square : public Rectangle { public: Square() {cout << "Constructing Square\n"; void SetSide(float); float GetSide() const {return Rectangle::GetWidth(); ~Square() {cout << "Deconstructing Square\n"; ; void Square::SetSide(float s) { Rectangle::SetWidth(s); Rectangle::SetHeight(s);

8 26. What is the relationship between the classes Rectangle and Square? a) Square has a Rectangle b) Square is a Rectangle c) Rectangle has a Square d) Rectangle is a Square e) none of the above Computer Science For the following code, what is the order in which the statements in the constructors and destructors for Square and Rectangle appear? { Square s; Rectangle r; a) Constructing Square b) Constructing Square Deconstructing Square Deconstructing Square c) d) Constructing Square Constructing Square Deconstructing Square Deconstructing Square e) none of the above 28. Which set of code will set the sides of a Square to be 4 and display the area? a) Square s; s.setwidth(4); s.sethieght(4); cout << s.getarea(); b) Square s; s.setside(4); cout << s.getside()*s.getside(); c) Square s; s.setside(4); cout << s.getarea(); d) all of the above e) none of the above

9 Computer Science Currently the Square class publicly inherits the Rectangle class. If the inheritance were to be changed to private, what methods would need to be added to the Square class in order for it to provide access to all of the same methods in which it can currently provide access? This change would be made by altering the declaration of the class from: class Square : public Rectangle { to: class Square : private Rectangle { a) No methods need to be added. b) GetArea, GetPerimeter c) GetArea, GetPerimeter, GetWidth, GetHeight d) GetWidth, GetHeight, SetWidth, SetHeight e) GetArea, GetPerimeter, GetWidth, GetHeight, SetWidth, SetHeight 30. Suppose the Square class was modified so that when the ++ operator was used with an object of type Square, the length of the sides of the square was increased by one. This would be an example of which of the following? a) Operator Overloading b) Inheritance c) Encapsulation d) Dynamic memory allocation e) all of the above