CS200 Spring 2004 Midterm Exam II April 14, Value Points a. 5 3b. 16 3c. 8 3d Total 100

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1 CS200 Spring 2004 Midterm Exam II April 14, 2004 Value Points a. 5 3b. 16 3c. 8 3d Total 100 Name StudentID#

2 1. [12 pts] Short Answer from recitations: a) [3 pts] What is the first line in a shell script? b) [3 pts] How would you archive the files in directory backup into file backup.tar using verbose output? c) [3 pts] What command would you use to print to the screen in a shell script? d) [3 pts] If I wanted to run a command line interactive program as a batch and I had put the commands to be input in a file called responses, modify the following command to redirect the contents of the file into standard input: java assign5 contacts messagelist spamlist oklist 2. [26 pts] Multiple Choice. Circle the letter of each statement that is true in each of the statements that follow the beginning statement. Note: there can be more than one or no true answers to each statement. a) Which of the following are true about stacks and queues? i) They are both linear, time-ordered structures. ii) Stack is FIFO and Queue is LIFO. iii) A wrap around array implementation of a queue provides the lowest Big O values for all operations provided you know how much space to allocate. b) Which are true about priority queues? i) It has methods: peek, enqueue and dequeue. ii) Worst case to add an element is O(n) when using either sorted or unsorted ArrayList implementation. iii) Provides access to the highest priority/minimum value, one element at a time. 26

3 c) Given the Binary Search Tree above, which of the following are true? i) If 10 is removed, then it is replaced by 6. ii) If 26 is removed, it is replaced by the 21 that is a leaf. iii) If 38 is removed, it is replaced by 29. iv) If 10 is added, it becomes the right child of 6. d) Which of the following is true about maps? i) A map creates a linear organization to maintain associations between keys and values. ii) A hash table provides close to constant time access because it is set up so that the location of the data is computed directly from the key for the majority of the keys. iii) A collision occurs when two different keys map to the same location. 3. Short Answer a) [5 pts] We did not discuss implementing an iterator or traversal for a heap. Aside from examining the contents for debugging, is there any reason to do so? Why or why not?

4 b) [16 pts] Fill in the array for the heap that results given the following heap and the commands that follow: Add 5 Remove Remove Add 21 c) [8 pts] In assignment 5, the word lists are implemented using a Binary Search Tree. Compare that approach (i.e., the Binary Search Tree) against storing them in an ArrayList which is searched using Binary Search. State one pro (reason why the Binary Search Tree is a better approach) and one con (reason why the Binary Search Tree is a worse approach). PROS CONS

5 d) [8 pts] Pick one of the data structures that can be used to implement a map (as listed in class). Name the underlying data structure that you have selected and fill out the following table of worst case Big-O values for the computation of the three operations and for the space required. Operation Data Structure Space Add Search Remove 4. [25 pts] Assuming you have code that implements the following interface for a BinaryTreeNode class, fill in the code for the constructor and Next method for an Iterator that performs an inorder traversal of a Binary Tree starting from the root. If you need to create other supporting methods, use the next page or back of this page. Assume that left, right and parent return null if there is none. public class BinaryTreeNode { public BinaryTreeNode(Object value) public BinaryTreeNode left() public BinaryTreeNode right() public BinaryTreeNode parent() public void setleft(binarytreenode newnode) public void setright(binarytreenode newnode) public void setparent(binarytreenode newnode) public Object value() public void setvalue(object newval) } public class BTIterator{ public BTIterator(BinaryTreeNode root) {

6 } public Object next() { }