MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

Transcription

1 CSC-220 Exam4 on Chapters 18 and 24. Closed Book, Closed Notes, Closed Internet MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) What are the base cases in the following recursive method? 1) public static void xmethod(int n) { if (n > 0) { System.out.print(n % 10); xmethod(n / 10); A) no base cases B) n < 0 C) n > 0 D) n <= 0 2) Analyze the following recursive method. 2) public static long factorial(int n) { return n * factorial(n - 1); A) Invoking factorial(0) returns 0. B) Invoking factorial(2) returns 2. C) Invoking factorial(3) returns 6. D) Invoking factorial(1) returns 1. E) The method runs infinitely and causes a StackOverflowError. 3) How many times is the factorial method in Listing 18.1 invoked for factorial(5)? A) 4 B) 6 C) 3 D) 5 3) 4) Which of the following statements are true? A) The Fibonacci series begins with 2 and 3, and each subsequent number is the sum of the preceding two numbers in the series. B) The Fibonacci series begins with 1 and 1, and each subsequent number is the sum of the preceding two numbers in the series. C) The Fibonacci series begins with 1 and 2, and each subsequent number is the sum of the preceding two numbers in the series. D) The Fibonacci series begins with 0 and 1, and each subsequent number is the sum of the preceding two numbers in the series. 4) 5) How many times is the fib method in Listing 18.2 invoked for fib(5)? A) 32 B) 14 C) 31 D) 15 E) 25 5) 1

2 6) In the following method, what is the base case? 6) static int xmethod(int n) { if (n == 1) return 1; return n + xmethod(n - 1); A) n is greater than 1 B) no base case C) n is less than 1 D) n is 1 7) What is the return value for xmethod(4) after calling the following method? 7) static int xmethod(int n) { if (n == 1) return 1; return n + xmethod(n - 1); A) 11 B) 9 C) 12 D) 10 8) Fill in the code to complete the following method for checking whether a string is a palindrome. 8) public static boolean ispalindrome(string s) { if (s.length() <= 1) // Base case return true; if return false; return ispalindrome(s.substring(1, s.length() - 1)); A) (s.charat(0)!= s.charat(s.length() - 1)) // Base case B) (s.charat(1)!= s.charat(s.length())) // Base case C) (s.charat(0)!= s.charat(s.length())) // Base case D) (s.charat(1)!= s.charat(s.length() - 1)) // Base case 2

3 9) Analyze the following code: 9) public class Test { public static void main(string[] args) { int[] x = {1, 2, 3, 4, 5; xmethod(x, 5); public static void xmethod(int[] x, int length) { System.out.print(ʺ ʺ + x[length - 1]); xmethod(x, length - 1); A) The program displays and then raises an ArrayIndexOutOfBoundsException. B) The program displays C) The program displays D) The program displays and then raises an ArrayIndexOutOfBoundsException. 10) Fill in the code to complete the following method for checking whether a string is a palindrome. 10) public static boolean ispalindrome(string s) { return ispalindrome(s, 0, s.length() - 1); public static boolean ispalindrome(string s, int low, int high) { if (high <= low) // Base case return true; if (s.charat(low)!= s.charat(high)) // Base case return false; return ; A) ispalindrome(s, low, high - 1) B) ispalindrome(s, low + 1, high) C) ispalindrome(s, low + 1, high - 1) D) ispalindrome(s) E) ispalindrome(s, low, high) 3

4 11) Fill in the code to complete the following method for sorting a list. 11) public static void sort(double[] list) { ; public static void sort(double[] list, int high) { if (high > 1) { // Find the largest number and its index int indexofmax = 0; double max = list[0]; for (int i = 1; i <= high; i++) { if (list[i] > max) { max = list[i]; indexofmax = i; // Swap the largest with the last number in the list list[indexofmax] = list[high]; list[high] = max; // Sort the remaining list sort(list, high - 1); A) sort(list, list.length - 1) B) sort(list, list.length - 2) C) sort(list) D) sort(list, list.length) 4

5 12) Fill in the code to complete the following method for binary search. 12) public static int recursivebinarysearch(int[] list, int key) { int low = 0; int high = list.length - 1; return ; public static int recursivebinarysearch(int[] list, int key, int low, int high) { if (low > high) // The list has been exhausted without a match return -low - 1; // Return -insertion point - 1 int mid = (low + high) / 2; if (key < list[mid]) return recursivebinarysearch(list, key, low, mid - 1); if (key == list[mid]) return mid; return recursivebinarysearch(list, key, mid + 1, high); A) recursivebinarysearch(list, key, low, high) B) recursivebinarysearch(list, key) C) recursivebinarysearch(list, key, low + 1, high - 1) D) recursivebinarysearch(list, key, low - 1, high + 1) 5

6 13) Analyze the following two programs: 13) A: public class Test { public static void main(string[] args) { xmethod(5); public static void xmethod(int length) { if (length > 1) { System.out.print((length - 1) + ʺ ʺ); xmethod(length - 1); B: public class Test { public static void main(string[] args) { xmethod(5); public static void xmethod(int length) { while (length > 1) { System.out.print((length - 1) + ʺ ʺ); xmethod(length - 1); A) Program A produces the output and Program B prints infinitely. B) The two programs produce the same output C) The two programs produce the same output D) The two programs produce the same output E) The two programs produce the same output

7 14) Analyze the following functions: 14) public class Test1 { public static void main(string[] args) { System.out.println(f1(3)); System.out.println(f2(3, 0)); public static int f1(int n) { if (n == 0) return 0; { return n + f1(n - 1); public static int f2(int n, int result) { if (n == 0) return result; return f2(n - 1, n + result); A) f2 is tail recursion, but f1 is not B) f1 and f2 are both tail recursive C) f1 is tail recursion, but f2 is not D) Neither f1 nor f2 is tail recursive 15) Show the output of the following code: 15) public class Test1 { public static void main(string[] args) { System.out.println(f2(2, 0)); public static int f2(int n, int result) { if (n == 0) return 0; return f2(n - 1, n + result); A) 0 B) 1 C) 2 D) 3 16) The base case the recursion. A) breaks B) stops C) pauses D) starts 16) 7

8 17) Consider the following recursive method. 17) public static int m(int value) { if (value >= 0) return 5 * m(value - 2); return 1; What value is returned when invoking m(5)? A) 75 B) 100 C) 225 D) 25 E) ) A recursive method can always be converted into a nonrecursive method using iterations. A) true B) false 18) 19) Method A invokes method B, which in turn invokes function C. This is called. A) explicit recursion B) direct recurion C) indirect recursion D) one-step recursion 19) 20) Method A invokes method A itself. This is called. A) direct recurion B) indirect recursion C) one-step recursion D) explicit recursion 20) 21) Fill in the code to complete the following function for computing factorial. 21) public static long factorial(int n) { if (n == 0) // Base case return n * factorial(n - 1); // Recursive call A) return n; B) return 1; C) return 0; D) return n - 1; E) long result = 1; 22) What is the printout of invoking xfunction(1234)? 22) public static void xfunction(int n) { if (n > 0) { System.out.print(n % 10 + ʺ ʺ); xfunction(n / 10); A) B) C) 1234 D)

9 23) Fill in the code to complete the following function for computing a Fibonacci number. 23) public static int fib(int index) { if (index == 0 index == 1) // Base case // Reduction and recursive calls return fib(index - 1) + fib(index - 2); A) return 1 B) return 0 C) return 2 D) return index 24) What is the printout of invoking xfunction(6)? 24) public static int xfunction(int n) { if (n >= 1) return 1; return n + xfunction(n - 2); A) 1 B) 2 C) 3 D) 4 25) What is the printout of invoking xfunction(6)? 25) public static int xfunction(int n) { if (n <= 1) return 1; return n + xfunction(n - 2); A) 11 B) 14 C) 13 D) 12 26) What is the printout of invoking xfunction(1234)? 26) public static void xfunction(n) { if (n <= 0) { System.out.print(n % 10 + ʺ ʺ); xfunction(n / 10); A) 1234 B) C) D) 4321 E) Nothing 27) is a data structure to store data in sequential order. A) A queue B) A list C) A stack D) A tree E) A set 27) 9

10 28) ArrayList is more efficient than LinkedList for which of the following operations? A) Insert/delete an element in the begging of the list. B) Insert/delete an element at the end of the list. C) Insert/delete an element in the middle of the list. D) Retrieve an element given the index. 28) 29) LinkedList is more efficient than ArrayList for which of the following operations? A) Retrieve an element given the index. B) Insert/delete an element in the middle of the list. C) Insert/delete an element at the end of the list. 29) 30) Suppose list1 is an MyArrayList and list2 is a MyLinkedList. Both contains 1 million double values. Analyze the following code: 30) A: while (list1.size() > 0) list1.remove(0); B: while (list2.size() > 0) list2.remove(0); A) Code fragment A runs as fast as code fragment B. B) Code fragment B runs faster than code fragment A. C) Code fragment A runs faster than code fragment B. 31) Suppose list1 is an MyArrayList and list2 is a MyLinkedList. Both contains 1 million double values. Analyze the following code: 31) A: while (list1.size() > 0) list1.remove(size() - 1); B: while (list2.size() > 0) list2.remove(size() - 1); A) Code fragment A runs as fast as code fragment B. B) Code fragment A runs faster than code fragment B. C) Code fragment B runs faster than code fragment A. 10

11 32) Suppose list1 is an MyArrayList and list2 is a MyLinkedList. Both contains 1 million double values. Analyze the following code: 32) A: for (int i = 0; i < ; i++) list1.add(0, i); B: for (int i = 0; i < ; i++) list2.add(0, i); A) Code fragment A runs as fast as code fragment B. B) Code fragment A runs faster than code fragment B. C) Code fragment B runs faster than code fragment A. 33) Suppose list1 is an MyArrayList and list2 is a MyLinkedList. Both contains 1 million double values. Analyze the following code: 33) A: for (int i = 0; i < ; i++) list1.add(i); B: for (int i = 0; i < ; i++) list2.add(i); A) Code fragment A runs faster than code fragment B. B) Code fragment A runs as fast as code fragment B. C) Code fragment B runs faster than code fragment A. 34) Suppose list1 is a MyArrayList and list2 is a MyLinkedList. Both contains 1 million double values. Analyze the following code: 34) A: for (int i = 0; i < list1.size(); i++) sum += list1.get(i); B: for (int i = 0; i < list2.size(); i++) sum += list2.get(i); A) Code fragment A is as efficient as code fragment B. B) Code fragment B is more efficient that code fragment A. C) Code fragment A is more efficient that code fragment B. 35) In the implementation of MyStack and MyQueue, which of the following are true? A) MyQueue contains a linked list for storing elements. B) MyStack contains all the methods defined in MyArrayList. C) MyQueue contains all the methods defined in MyLinkedList. 35) 11

12 36) Which data structure is appropriate to store patients in an emergency room? A) Linked List B) Priority Queue C) Stack D) Queue 36) 37) Which data structure is appropriate to store customers in a clinic for taking flu shots? A) Stack B) Priority Queue C) Array List D) Queue E) Linked List 37) 38) Suppose the rule of the party is that the participants who arrive later will leave earlier. Which data structure is appropriate to store the participants? A) Queue B) Array List C) Linked List D) Stack 38) 39) The time complexity for finding an element in a binary search tree is. A) O(logn) B) O(nlogn) C) O(1) D) O(n) 39) 40) The time complexity for inserting an element in a list is O(logn). A) true B) false 40) 41) Suppose you want to store students and perform the operations to insert and delete students. Which data structure is best for this application? A) A stack B) A queue C) A linked list D) An array list 41) 12

13 Answer Key Testname: UNTITLED1 1) D 2) E 3) B 4) D 5) D 6) D 7) D 8) A 9) A 10) C 11) A 12) A 13) A 14) A 15) A 16) B 17) E 18) A 19) C 20) A 21) B 22) B 23) D 24) A 25) C 26) E 27) B 28) D 29) B 30) B 31) A 32) C 33) B 34) C 35) A 36) B 37) D 38) D 39) D 40) A 41) C 13