CS 2420 ? Fall 2010 Priority Queues (Heaps) Priority Queue

Objective: Implement a priority queue.
Priority Queue
CS 2420 – Fall 2010
Program 5 – 20 points
Priority Queues (Heaps)
A max priority queue is a data structure that allows at least two operations: insert which does the
obvious thing and deleteMax, that finds, returns, and removes the maximum element in the
priority queue. The max priority queue will be implemented as a binary heap (a table which
logically represents an almost complete binary tree).
The data you will use to test this priority queue is the concordance you produced in program 4.
If you didn’t complete that program, you can just input a copy of the output file from program 4
(prog5.txt). Make sure your array is large enough to hold all the words.
You are to insert all the data (word and occurrenceCt) into the priority queue and then delete
them one at a time (to produce a sorted list). (This is actually an unimpressive way of using a
priority queue, as the priority queue can handle interleaved insertions and deletions.)
The output will be the entire concordance with the most commonly used word(s) and number of
occurrences listed first, and the least commonly used word(s) and number of occurrences listed
last. Be sure to send the output to a file, prog5out.txt.
When you have completed the assignment, zip your entire project and submit the zip file to
Eagle.
Hints:
While combining this program with your hash table code is "logically appealing", just reading in
prog5.txt is simpler.
prog5.txt is HUGE. We need to see output created from this file, but test your program with a
very small file.
To do reasonable debugging, I like to have every data structure know how to print itself. In
particular, the entries in the queue need to be able to print themselves. In Java, a function which
prints the data structure is called "toString" – so I use that convention. In C++, being able to
create a string from various data types is not easy. Below is a clever trick to accomplish this
goal. Basically, you create a string stream which acts like a stream (using regular

class ItemType
{ public:
string word;
int occurrenceCt;
int key;
ItemType(string aword = "", int ct=0) { word = aword; occurrenceCt=ct; key = ct;}
string toString() {
stringstream out;
out