Read about the code style principles. From this assignment on, you should follow the code style principles detailed in this page. Read it carefully or you might lose points in grading.
Write a generic data type for a deque and a randomized queue. The goal of this assignment is to implement fundamental collections using resizing arrays and linked lists, and to introduce you to generics and iterators.Dequeue. A double-ended queue or deque (pronounced “deck”) is a generalization of a stack and a queue that supports adding and removing items from either the front or the back of the collection. Create a generic data type Deque that implements the following API:
public class Deque<Item> implements Iterable<Item> { // construct an empty deque public Deque() // is the deque empty? public boolean isEmpty() // return the number of items on the deque public int size() // add the item to the front public void addFirst(Item item) // add the item to the back public void addLast(Item item) // remove and return the item from the front public Item removeFirst() // remove and return the item from the back public Item removeLast() // return an iterator over items in order from front to back public Iterator<Item> iterator() // unit testing (required) public static void main(String[] args)
}
Corner cases. Throw the specified exception for the following corner cases:
- Throw an IllegalArgumentException if the client calls either addFirst() or addLast() with a null argument.
- Throw a java.util.NoSuchElementException if the client calls either removeFirst() or removeLast when the deque is empty.
- Throw a java.util.NoSuchElementException if the client calls the next() method in the iterator when there are no more items to return.
Unit testing. Your main() method should implement the following tests:
- Create a deque of integers and add the numbers 1 through 10 to the deque using addFirst(), and then remove them all using removeLast(). Verify that the output of the removals is the numbers 1 through 10 (in this order), e.g., by printing "Error" to the standard output if you find a discrepancy.
- Repeat the same test as the above, but using addLast() and removeFirst().
- Create a deque of integers and add the numbers 1 through 10 to the deque using addFirst(). Use a foreach loop to print the contents of the deque. Verify that the output is the number 10 through 1 (in this order).
Note that the unit tests won't be graded by the tigerfile autograder, they will be manually graded. So you don't have to follow any specific format, but you also won't get automatic feedback on it when you click on "Check Submitted Files".
Performance requirements. Your implementation must achieve the following worst-case performance requirements:
- A deque containing n items must use at most ~48n bytes of memory, not including the memory for the items themselves.
- Each deque operation (including construction) must take constant time.
- Each iterator operation (including construction) must take constant time.
Randomized queue. A randomized queue is similar to a stack or queue, except that the item removed is chosen uniformly at random among items in the collection. Create a generic data type RandomizedQueue that implements the following API:
public class RandomizedQueue<Item> implements Iterable<Item> { // construct an empty randomized queue public RandomizedQueue() // is the randomized queue empty? public boolean isEmpty() // return the number of items on the randomized queue public int size() // add the item public void enqueue(Item item) // remove and return a random item public Item dequeue() // return a random item (but do not remove it) public Item sample() // return an independent iterator over items in random order public Iterator<Item> iterator() // unit testing (optional) public static void main(String[] args)
}
Iterator. Each iterator must return the items in uniformly random order. The order of two or more iterators to the same randomized queue must be mutually independent; each iterator must maintain its own random order.
Corner cases. Throw the specified exception for the following corner cases:
- Throw an IllegalArgumentException if the client calls enqueue() with a null argument.
- Throw a java.util.NoSuchElementException if the client calls either sample() or dequeue() when the randomized queue is empty.
- Throw a java.util.NoSuchElementException if the client calls the next() method in the iterator when there are no more items to return.
Unit testing. You don't need to create unit tests for the randomized queue.
Performance requirements. Your implementation must achieve the following worst-case performance requirements:
- A randomized queue containing n items must use at most ~48n bytes of memory, not including the memory for the items themselves.
- Each randomized queue operation (besides creating an iterator) must take constant amortized time. That is, starting from an empty randomized queue, any intermixed sequence of m such operations must take \(\Theta(m)\) time in the worst case. Θ(m)Θ(�) time in the worst case.
- An iterator over n items must at use at most ~8n bytes of memory.
- Constructing an iterator must take \(\Theta(n)\) time; the Θ(n)Θ(�) time; the next() and hasNext() operations must take constant time.
Client. Write a client program Permutation.java that takes an integer k as a command-line argument; reads a sequence of strings from standard input using StdIn.readString(); and prints exactly k of them, uniformly at random. Print each item from the sequence at most once.
Your program must implement the following API:
public class Permutation {
public static void main(String[] args)
}
Command-line argument. You may assume that 0 ≤ k ≤ n, where n is the number of string on standard input. Note that you are not given n.
Performance requirements. Your implementation must achieve the following worst-case performance requirements:
- The running time of Permutation must be must be linear in the size of the input.
- You may use only a constant amount of memory plus either one Deque or RandomizedQueue object with at most n items.
- For an extra challenge (and a small amount of extra credit), use only a constant amount of memory plus either one Deque or RandomizedQueue object with at most k items.
Submission. Submit the programs RandomizedQueue.java, Deque.java, and Permutation.java. Your submission may not call library functions except those in StdIn, StdOut, StdRandom, java.lang, java.util.Iterator, and java.util.NoSuchElementException. In particular, do not use either java.util.LinkedList or java.util.ArrayList. Finally, submit readme.txt and acknowledgments.txt files and answer the questions.
Grading.
file points Deque.java 18 RandomizedQueue.java 15 Permutation.java 5 readme.txt 2 40
Reminder: You can lose up to 4 points for breaking style principles and up to 3 points for not implementing the deque unit tests.
Extra credit: You can earn 2 points of extra credit for conserving memory in Permutation.java (see performance requirements section above).