CSE 114 Midterm 1. Please leave one seat between yourself and each of your neighbors.

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1 CSE 114 Midterm 1 Please leave one seat between yourself and each of your neighbors. Please place ALL of your final answers on the answer sheet that you were given at the start of the exam. Answers and other information written on this question packet will NOT be graded. The problems in this exam are not necessarily ordered by difficulty, so be sure to look through the entire exam before starting. This exam is CLOSED-BOOK, CLOSED-NOTES. You may NOT use any computers, calculators, smartphones, or any other electronic or manual aids during the exam. The presence of any such devices or notes will be treated as evidence of academic dishonesty. The last page of this question packet contains some helpful reference information. Feel free to tear that page off for your convenience while taking the exam. Any CHEATING will result in a 0 for the exam, as well as charges of academic dishonesty. Do not: 1. interact with (for example, speak to) your neighbors during the exam, or 2. place anything in a location where it may appear that you are sharing information or copying (or allowing others to copy your work)! Please raise your hand or come to the front of the room if you have any questions during the exam. When you are finished, please return both your answer sheet AND your question packet to the instructor and TAs. You must present photo ID (student ID, driver s license, etc.) when submitting your final work. The score for a perfect exam is 150 points. DO NOT BEGIN WORK UNTIL YOU ARE TOLD TO DO SO!

2 1. Translate the three values below into base 10, and then identify the one whose value is different from the others (or select None of the above if all three base 10 values are identical). A. 111 (base 8) B. 221 (base 5) C. 141 (base 6) D. None of the above (all three values are identical in base 10) 2. What is the hexadecimal equivalent of the unsigned binary value ? A. 7D5 B. FBA C. 3ED D. None of the above 3. The hexadecimal value AC represents an unsigned binary value. Translate this value into base What will the following sequence of statements print? (3 points each) (15 pts) int a = 3, b = 4, c = 5; double d = 10.0, e = 2.0, f = 7.0; System.out.println((a * c) % b); // This is answer 'a' System.out.println(d / (a + e)); // This is answer 'b' b++; System.out.println(b * --c); // This is answer 'c' System.out.println(d / e + f); // This is answer 'd' if (d < e + f) // One of the statements below provides answer 'e' System.out.println(a * f); else System.out.println(b); Stony Brook University Page 1

3 5. Consider the following Java code fragment. What values will it print? int [ ] foo = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 ; for (int x = 1; x < 11; x += 3) System.out.print(foo[x] + " "); A B C D E What will the code fragment below print? String c = "candy"; for (int i = 4; i > 1; i--) System.out.print(c.charAt(i)); System.out.println(); A. cand B. andy C. ydn D. ydna E. ydnac 7. How many times will the following loop print "Waiting..."? for (int val = 3; val < 33; val += 5) if (val % 2 == 1) System.out.println("Waiting..."); A. 5 B. 6 C. 7 D. 3 E. None of the above Stony Brook University Page 2

4 8. The code below prints out a series of asterisks. How many asterisks will it print in all? int x = 0; while (x < 6) for (int y = 0; y <= x; y++) System.out.print("*"); System.out.println(); x++; A. 5 B. 6 C. 21 D. 36 E. None of the above 9. What will the method below return for the input "pompeii"? public static String mystery (String text) String result = ""; for (int i = 0; i < text.length(); i++) if (text.charat(i) == 'p') result += "pop"; else if (text.charat(i) == 'm') result = ""; else result += text.charat(i); return result; A. "popompopeii" B. "po" C. "mpopeii" D. "popeii" E. "eii" Stony Brook University Page 3

5 10. Consider the following code fragment: for (int i = 1; i <= 10; i++) for (int j = 1; j <= 10; j++) System.out.print("1"); System.out.println(); How many lines of output will be printed in all? A. 1 B. 10 C. 20 D. 100 E. None of the above 11. What s wrong with the following switch statement? // Assume that variables 'ranking' and 'pay' have already been declared and initialized switch (ranking) case > 4.55: pay = pay *.20; break; case == 4.55: pay = pay * 30; default: break; A. The switch statement does not need the brackets. B. The default case does not contain any statements other than break. C. Each break statement should appear on a line by itself. D. Boolean operators are not allowed in the case labels. 12. Rewrite the following for loop as an equivalent while loop. (8 pts) double rate = 0.05, amt = ; for (int year = 1; year <= 5; year = year + 1) amt = amt + (amt * rate); System.out.println("Year " + year + " amount is " + amt); Stony Brook University Page 4

6 13. For each of the following code fragments, BRIEFLY explain what error is present (or write NO ERROR if there is no error) on the answer sheet. BE CAREFUL! (a) float[ ] f = 1.1, 10.01, , ; (b) public class MyClass public static int foo (int x) return x; public static void foo (String w) System.out.println(w.length()); public static void foo (int y) System.out.println(y); (c) public static void main(string[] args) int max = getmaxofthree(3,4,5); System.out.println("Largest value is " + max); public static int getmaxofthree(int x, int y, int z) if (x > y) if (x > z) return x; else return z; else if (y > z) return y; else return z; (d) int [] x = new int[20]; for (int i = 19; i >= 0; --i); x[i] = i * i; System.out.println("x[" + i + "] = " + x[i]); 14. The following sequence of Java statements: String first = "Hello, world!"; String second = "Hello,"; second = second + " world!"; System.out.println(first == second); prints out false, when we would expect it to print true instead. On the answer sheet, briefly explain this result. Stony Brook University Page 5

7 15. The method below processes a String containing only a s, b s, and c s as it moves between rows in the transitions array. Each letter corresponds to a column in this array; each array element indicates the row to use for the next character. As the method executes, it prints out the index of each new row that it visits. For example, given the input "abca", this method would print "1234". public static void process (String input) int row = 0; int [][] transitions = 1, 0, 2, 1, 2, 0, 1, 0, 3, 4, 3, 3, 4, 5, 3, 4, 3, 0 ; (a) for (int i = 0; i < input.length(); i++) char c = input.charat(i); int col = (int) (c - 'a'); // e.g., 'a' maps to 0 row = transitions[row][col]; System.out.print(row); What will this method print for the argument "abaa"? (b) (c) What will this method print for the argument "babcabc"? What will this method print for the argument "abcabbabcab"? 16. Consider the following Java method definition: public static String mystery (String text) // Assume text is all-lowercase String result = ""; int [] count = new int[26]; for (int i = 0; i < count.length; i++) count[i] = 0; for (int index = 0; index < text.length(); index++) char c = text.charat(index); int p = (int)(c - 'a'); count[p]++; for (int n = 0; n < count[p]; n++) result += c; (a) (b) return result; What does mystery() return for the argument "tutu"? What does mystery() return for the argument "database"? Stony Brook University Page 6

8 17. A narcissistic number is an integer that is equal to the sum of its own digits, each of which has been (8 pts) raised to the power of the total number of digits. For example, (which is 5 digits long) is narcissistic because = = Complete the isnarcissistic() method. This method takes a single (positive, non-zero) integer argument, and returns a boolean value (either true or false) indicating whether the argument is a narcissistic number as defined above. For example: isnarcissistic(15); returns false because 15 is not narcissistic ( = (1 + 25) = 26, and 26 15). 18. Assume that you are located at an arbitrary index in an array filled with positive integer values. You (10 pts) must navigate back and forth through the array according to the following rules: If your current array index is composite (i.e., not a prime number), look at the value stored in that array position and move to that index in the array (for example, if you are located at index 6, and that array index contains the value 3, move to index 3). Otherwise (you are standing on an array index that is prime), look at the value stored in that array position and move that many indexes back (towards 0). For example, if you were standing at array index 7 (which is prime) and the value stored at that array index was 3, you would move 3 positions back, ending at index 4. Once you reach an invalid index (one that is outside the bounds of the array), you have successfully escaped. Complete the escape() method, which takes two arguments: an array of integers and an integer representing your starting index within that array. The method returns an integer representing the total number of moves required to escape the array. Assume that you have been given a method named isprime() that returns true if its integer argument is prime and false if it is not. Assume that your starting index is within the bounds of the array, and that you will always (eventually) escape the array. 19. Complete the flatten() method, which takes a two-dimensional array of integers as its argument. The (12 pts) method returns a one-dimensional integer array that contains all of the elements from the argument, in row order (in other words, all of the elements from the first row of the argument, followed by all the elements of the second row, etc.). You MAY NOT assume that the argument array is square; each row may have a different length! For example, given the array 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, your method should return the array 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14. Stony Brook University Page 7

9 20. On the social media network Twitter, a single post (tweet) is restricted to 140 characters in length (this (15 pts) is now changing to 280 characters). A tweetstorm is a sequence of numbered tweets that, taken together, convey a message that exceeds the length of a single tweet. Complete the tweetstorm() method on the answer sheet. This method takes a single String argument representing a complete message. The method should break up its argument into one or more smaller strings of 130 characters or less (to allow room for a sequence number, although we won t add that right now) and print those strings, one at a time, to standard output using System.out.println(). Each tweet generated by your method should respect word boundaries, meaning that you need to break up the original message based on spaces instead of just cutting after every 130th character. When the entire tweetstorm has been printed, your method should return an integer representing the total number of tweets that were generated. For example, consider the following variable assignment in Java: String source = "The 28th Disney animated feature film, The Little Mermaid was released to theaters on November 17, 1989 to largely positive reviews, garnering $84 million at the domestic box office during its initial release, and $211 million in total lifetime gross worldwide. After the success of the 1988 Disney/Amblin film Who Framed Roger Rabbit, The Little Mermaid is given credit for breathing life back into the art of Disney animated feature films after a string of critical or commercial failures produced by Disney that dated back to the early 1970s. It also marked the start of the era known as the Disney Renaissance."; The method call tweetstorm(source); would produce output similar to the following: The 28th Disney animated feature film, The Little Mermaid was released to theaters on November 17, 1989 to largely positive reviews, garnering $84 million at the domestic box office during its initial release, and $211 million in total lifetime gross worldwide. After the success of the 1988 Disney/Amblin film Who Framed Roger Rabbit, The Little Mermaid is given credit for breathing life back into the art of Disney animated feature films after a string of critical or commercial failures produced by Disney that dated back to the early 1970s. Renaissance. It also marked the start of the era known as the Disney and would return the integer 5, since the tweetstorm contained five smaller tweets in all. HELPFUL HINTS 1. A while loop and the String methods charat() and substring() are essential here! 2. When searching for the end of a smaller tweet element, if you have more than 130 characters left, start by looking 130 characters ahead of your current position within the string. Decrement your index until it points to a space character (indicating that you have reached a word boundary). Don t print leading spaces at the beginning of each new tweet! Stony Brook University Page 8

10 The String class REFERENCE INFORMATION charat(n) Returns the character at index n. Indices are numbered from 0-(length-1). length() Returns the number of characters contained in the current String. tolowercase() Returns an all-lowercase version of the current String. touppercase() Returns an all-uppercase version of the current String. substring(i, j) Returns a new String containing the characters from index i up to, but not including, index j. substring(i) Returns a new String containing the characters from index i through the end of the String. indexof(s) Returns the index of the first occurrence of the String s in the current String, or -1 if it cannot be found. equals(s) Returns true if its argument matches the current String exactly, including case (compare to the equalsignorecase() method). The Math class abs(x) Returns the absolute value of x. max(x, y) Returns the larger of x and y. min(x, y) Returns the smaller of x and y. pow(b, e) Raises b to the e-th power. random() Returns a random double from 0.0 up to (but not including) 1.0. round(x) Rounds x to the nearest integer value. sqrt(x) Returns the square root of x, where x 0. Selected Numerical Values in Assorted Bases Quantity Binary (Base 2) Octal (Base 8) Decimal (Base 10) Hexadecimal (Base 16) Zero One Two Three Four Five Six Seven Eight Nine Ten A Eleven B Twelve C Thirteen D Fourteen E Fifteen F Sixteen Stony Brook University Page 9