Download COS 126 Fall 2006 Exam 1 Solutions: Short Answers, Arrays, Functions, Loops, Strings, I/O, and more Exams Computer Science in PDF only on Docsity!
COS 126 Fall 2006 Exam 1 Solutions
- Short Answer (a) - 20 (b) 3. (c) - 2^31 = - 2147483648 (d) Infinity (e) 6.022e
- Arrays, Conditional, Loops, and Bugs
- MainProgram instead of main
- did not allocate elements of array a
- keepOn should be initialized to true
- in the for loop inside the while loop, go to N- 1 instead of N
- temp should be a double, not an int
- order is wrong in the swap statements
- missing semicolon after increment of iters
- Functions My score will be 9.5 points. This question is worth 10 points. Of all the 9.5 points, I will receive 10 of them.
- Loops, Strings, Conditionals (a) 31+121+ 1/1/1/1/ 2/+/3/ 1/ StringIndexOutOfBoundsException: (or the equivalent)
(b) 2N^ (because the string length doubles at each iteration)
- I/O public static void findClosest(double X) { double closest = StdIn.readDouble(); while (!StdIn.isEmpty()) { double next = StdIn.readDouble(); if (Math.abs(X - next) < Math.abs(X - closest)) closest = next; } System.out.println(closest); }
- Recursion
computes "n + 1" In general, Ack(1, n) = Ack(0, Ack(0, ........ Ack(1, 0))), with "n" Ack(0, ...) and one Ack(1, 0). Since Ack(1, 0) is 2, and the other "n" Acks add 1 onto the previous result, we get n + 2. (c) Ack(2, 0) = Ack(1, 1) = 3 Using the fact that Ack(1, n) = n + 2. Ack(2, 3) = Ack(1, Ack(2, 2)) = Ack(1, Ack(1, Ack(2, 1))) = Ack(1, Ack(1, Ack(1, Ack(2, 0)))) = 2 + 2 + 2 + 3 = 9 Using the facts that Ack(2, 0) is 3 and that Ack(1, n) computes "n + 2". Ack(2, 6) = Ack(1, Ack(2, 5)) = Ack(1, Ack(1, Ack(2, 4))) = Ack(1, Ack(1, Ack(1, Ack(2, 3)))) = 2 + 2 + 2 + 9 = 15 Using the fact that Ack(2, 3) is 9 and that Ack(1, n) computes "n + 2". In general, Ack(2, n) = Ack(1, Ack(1, .... Ack(2, 0))), with "n" Ack(1, ....) and one Ack(2, 0). Since Ack(2, 0) is 3 and the other "n" Acks add 2 onto the previous result, we get 2n + 3.
- TOY All of these are no-ops (most use register 0): 10XY, 1XX0, 1X0X, 20XY, 2XX0, 30XY, 3XXX, 40XY, 4XX0, 4X0X, 50XY, 5XX0, 60XY, 6XX0, 70XY, 80XY, A0XY, D0XY (where X and Y are arbitrary nybbles)
