CS230 Data Structures Handout # 18
Prof. Lyn Turbak March 19, 2004
Wellesley College
Problem Set 6
Due: 6pm Friday, April 2
Overview:
The purpose of this assignment is to give you practice with implementing collections via linear
structures.
Working Together:
If you worked with a partner on a previous problem set and want to work with a partner on this
assignment, you are encourage to choose a different partner. However, you may also work with
someone you worked with in the first half of the semester.
Submission:
Each team should turn in a single hardcopy submission packet for all problems by slipping it
under Lyn’s office door by 6pm on the due date. The packet should include:
1. a team header sheet (see the end of this assignment for the header sheet) indicating the time
that you (and your partner, if you are working with one) spent on the parts of the assignment;
2. For Problem 1, your hardcopy submission should be your final versions of MaxPQArray.java
and MinPQArray.java, your testing transcripts showing that these work as expected.
3. For Problem 2, your hardcopy submission should be your final version of QueueCircular.java,
and your testing transcripts showing that it works as expected.
Each team should also submit a single softcopy (consisting of your final ps5 directory) to the
drop directory ~cs230/drop/ps5/username, where username is the username of one of the team
members (indicate which drop folder you used on your hardcopy header sheet). To do this, execute
the following commands in Linux in the account of the team member being used to store the code.
cd /students/username/cs230
cp -R ps5 ~cs230/drop/ps5/username/
Problem 1 [55]: Representing Priority Queues as Arrays
We saw in class that arrays can be used to efficiently implement arbitrary sized collections as
long as a size instance variable is used to hold the number of collection elements in the array
stored in the elts instance variable. Slots with indices 0 through elts.size - 1 hold the elements
of the collection, while slots size through elts.length hold “garbage elements” that can safely
be ignored. When size =elts.length, any attempt to add a new element to the collection must
increase the size of the array. As discussed in class, it’s a good idea to double the size of the array
in these cases to make such events rare.
In this problem, you will be implementing priority queues as arrays. This is very similar to
the exercise you had in lab of implementing priority queues in terms of vectors. Indeed, vectors
themselves are usually implemented as arrays in the manner described above.
a. [45]: MaxPQArray
In this problem, you are to flesh out an implementation of MaxPQ that represents a priority queue
using three instance variables:
1
