Gettysburg College Department of Computer Science

Transcription

1 Gettysburg College Department of Computer Science CS 111 Exam 1 Oct 6, 2014 This exam is closed-book, closed-notes, closed-computers, closed-internet, closed-calculators, closed-devices, and closed-neighbors. Show your work in each problem for full credit. NO variables outside methods are allowed and you are NOT to change/update the input parameters. Name: Honor Code and Signature: signature 1

2 Q1. Java Expressions (16 points) Given, int f(int x) { return (x - 5); int a = 30; int b = 5; double c = 20.0; Question Possible Your score Total 73 int x = 50; String s = DRJAVA ; give the value stored in the variables after the following assignments. (a) boolean bb =!(a <= b) ( ((a b) / c) <= ((a + b) / c) ); (b) double d = c / b + a; (c) int e = b / a; (d) double f = (c + a) / b; (e) int y = f(a) + f(b); (f) int z = f(x) ; (e) int len = s.length(); (f) char letter = s.charat(2); 2

3 Q2. Short Answers (8 points) (a) What is the Unix/Linux command to change folder (directory)? (b) How do you ask a user to enter a whole number between 50 and 100 and save user s answer in a new variable called input? Write a one-line code. (c) Give the exact output of the following Java code fragment. int a = 5; if (a >= 5) { System.out.printf( zero\n ); if (a < 10) { System.out.printf( one\n ); else if (a < 8) { System.out.printf( two\n ); else { System.out.printf( three\n ); System.out.printf( four\n ); if (a <= 5) { if (a < 10) { System.out.printf( five\n ); else { System.out.printf( six\n ); System.out.printf( seven\n ); 3

4 Q3. Detecting Errors (12 points) import Graphics; Class Mystery { void drawmystery(n) ; { Canvas.DrawCircle[300, 300, 300]; i = n; while (i => 0) Canvas.DrawRect[300, 300, 100 * i, 100 * i]; i = i 1; void test() ; { drawmystery[4] void Main (String args) ; { New Mystery.test(); (a) Clearly mark and correct all errors. (b) What would be drawn on the canvas when the corrected program is run?

5 Q4. While Loop Code Trace (8 points) Line 01: int j = 1; Line 02: int k; Line 03: int result = 10; Line 04: Line 05: while (j < 6) { Line 06: if ( (j % 2) == 1 ) { Line 07: k = j 1; Line 08: Line 09: else { Line 10: k = j + 1; Line 11: Line 12: Line 13: Line 14: Line 15: result = result - k; Line 16: j = j + 1; Line 17: Line 18: Line 19: System.out.printf( j = %d k = %d\n, j, k); System.out.printf( result = %d\n, result); (a) What are the values of j and k after the while loop is finished (at line 18)? j = k = (b) Exactly how many times is the loop body executed? Show your work. (c) Give the exact output of the code. 5

6 Q5. Writing Methods (29 points) NO DRAWING, NO PRINTING! (a) Write a method, square, which takes one double number and returns the square of the number. For example, square(2.0) returns 4.0 (2.0 * 2.0) and square(-3.0) returns 9.0. You are allowed to use only arithmetic and assignment operators for this problem. (3 points) (b) Write a method, distancesquare, which takes four double numbers representing two points (x1, y1) and (x2, y2) and returns the square of Euclidean distance between them, i.e., (x2 x1) 2 + (y2 y1) 2. You must use the square function you wrote in part (a) for full credit. (4 points) For example, square of Euclidean distance between p1 (80.0, 100.0) and p2 (100.0, 90.0) is distancesquare(80.0, 100.0, 100.0, 90.0) should return = =

7 (c) Write a method, calcbmr, which computes and returns basal metabolic rate, amount of daily energy used by a person at rest, based on four parameters: sex (1: woman, 2: man), weight (in kg), height (in cm), age and calculated as follows: (5 points) woman: ( 9.6 x weight_in_kilos ) + ( 1.8 x height_in_cm ) - ( 4.7 x age ) man : 66 + ( 13.7 x weight_in_kilos ) + ( 5 x height_in_cm ) - ( 6.8 x age ) E.g., calcbmr(2, 60, 176, 20) returns for a 20 year old male who is 176cm tall and weighs 60kg. (d) Write a method, printdivisible, which takes three integer parameters denom, a, and b, and prints all numbers between a and b that are divisible by denom, one number per line. (5 points) System.out.printf( %d\n, ); will print the value of in integer format. E.g., printdivisible,(4, 2, 13) will print 4, 8, 12; one number per line. 7

8 (e) Write a method, calcm, which takes a positive integer n and returns the calculation of the following Taylor series. For example, calcm(3) should calculate the first 3 terms and return the sum of them. Assume the existence of fact(n) = n! (as done in class). (6 points) (f) Write a method, addfiller, which takes a String str and an integer n and returns a new String which has all letters from str in the same order as they appear in str but with n after every two letters. For example, addfiller( HELLO, 2) returns HE2LL2O. (6 points) 8