Radix Sort Program

(Latest Revision: 02/29/2004)

Radix Sort: Using Queues and Structured Data

RATIONALE:

Writing this program will give you exposure to an advanced sorting algorithm, practice using queues in a non-trivial application, and an opportunity to invent additional data structures to suit the needs of the problem at hand.

THE ASSIGNMENT:

Write a program that

implements a queue data type whose elements are arrays of eight characters,
implements a set of ten of the above-described queues, giving random access to each queue in the set, and
uses the queue set to do a radix sort of a non-empty series of eight-digit non-negative integers.

INPUT:

The input will consist of a series of one or more lines of text. The text on each line will consist of one eight-digit integer, left justified. Each integer will be non-negative. Each integer will have exactly eight digits -- no more, no less.

The program will read all input from standard input.

SAMPLE INPUT:

OUTPUT:

The program will sort the numbers into ascending order and print the sorted list to standard output. The output will be formatted identically to the input.

SAMPLE OUTPUT:

HOW THE USER WILL OPERATE THE PROGRAM:

Suppose the executable program is called rsort. If the user wants to enter the input from the keyboard, s/he just enters the command:

rsort

and then enters the desired series of integers. When finished entering data the user presses the enter key and makes a control-D to signal the end-of-input.

Suppose the user wants the input to come from a prepared file called input01. In that case s/he just enters:

rsort < input01

In this case, where redirection of standard input to a file is done, there is no need to enter the end-of-input signal.

The user may wish to save the output of the program to a file. In that case, s/he can use this command:

rsort < input01 > output01

When I test your program, I will test it on several prepared files. Some input files will contain a large quantity of integers to sort. Other files will be small.

THE ALGORITHM:

There are ten queues: queue[0], queue[1], ..., queue[9].

Each input integer is a eight-digit number. The radix sort makes one pass for each of these eight digits.

The first pass sorts according to the least significant digit (ones-digit). In this pass, the program inserts each number into the queue corresponding to the number's least significant digit. In the 7 succeeding passes the program takes numbers off the queues and re-queues them according to their "tens-digit", "hundreds-digit", and finally their most significant digit ("ten-millions-digit"). When it performs one of these passes the program first takes all the elements from the previous pass off queue[0] and re-queues them. It then does the same thing for queue[1], queue[2], and so on, up to queue[9]. After the eighth and final pass, the program dequeues the numbers and writes them to the output. They come out in sorted order. (If you are "still confused" you can look at this example. I'll discuss the example in class.)

Besides the queue set and a single integer variable to use as an input buffer, your program will not need any additional storage to hold the integers to be sorted. Immediately after inputting each individual integer, the program may enqueue it according to the value of its ones-digit. After the last pass of the sort is complete the integers will be in the queues, distributed according to their "ten-millions-digit". The program can then write the sorted list to the standard ouput merely by emptying the queues, starting at the 0-queue and proceeding in numerical order to the 9-queue.

One element is still missing from the description of the algorithm. Since the program takes integers out of queues and re-enqueues them into the same set of queues, we enqueue a marker in each queue before beginning a new pass. When the program dequeues a marker, it knows that it has finished dequeueing all the integers that were in that queue at the start of the pass. For the marker, you may choose any eight-character array that cannot be confused with a list element. For example, the array ZZZZZZZZ could be the marker.

IMPLEMENTATION OF THE NUMBERS AND QUEUES:

The program must read each eight-digit integer as a sequence of eight characters, not as an integer variable. The program must internally represent each eight-digit integer as an array of eight characters. The program has to select individual digits from each integer as part of the sort. The value of the digit determines which queue the integer will be inserted into next. When we represent the integers as arrays of characters, it makes it particularly easy to perform this digit selection.

Use a linked list implementation of the queue data type. I recommend that you use the header and implementation files that are in this directory. You will have to define an itemClass in an item.h file or modify the QueueP.h file slightly to make the queue element type an array of eight characters.

Since there are ten related queues to be implemented, they must be organized into an appropriate data structure. An array of ten queues will work well.

ADDITIONAL SPECIFICATIONS:

Before you do any assignment for me, you need to read the programming assignment rules. This document contains my general rules regarding form, and style. The document also describes my grading criteria.

You also need to reference the other documents here: http://www.cs.csustan.edu/~john/Classes/General_Info/progAsgRules/ to make sure you are correctly applying the top-down design methodology and to make sure that you are including everything necessary in the programs and scripts you send me.

HELP WITH TESTING:

There is a makeList program in this directory that you can use to generate lists of integers to sort.

When you test the algorithm on a long list of integers you can use the unix sort and diff commands to verify that your program sorted the list correctly.

For example, suppose that you have a file called data containing 1000 integers in random order. Suppose that the name of your executable radix sort program is rsort. if you execute the following commands


rsort < data > myoutput
sort -n < data > sortoutput
diff myoutput sortoutput

then rsort sorted the numbers correctly if and only if diff found no differences between myoutput and sortoutput. (When there are no differences between the files, diff has no output at all, or possibly just some blank lines.)

I expect to see your use of rsort and diff in the test scripts you make.

MORE HELP:

Come to class to get help and hints.

WHAT TO TURN IN:

You will turn in two "phases" of this assignment:

a level 2 version, and
a final version.

For each phase of the assignment, you will turn in a printer output (hardcopy) and you will send me an e-mail message. Please follow these rules:

Always send me e-mail as plain text in the main message body. Never send me attachments.
Always use the exact subject line I specify for each message. (I often get hundreds of e-mail messages in a week. The subject line allows me to find, filter and sort messages.) You will lose a significant number of points on the assignment if you use the wrong subject line.
Be very careful when you send the e-mail. You may use the instructions in your Hello World! lab excercise for guidance. Of course, you will need to make the obvious changes to those directions -- you have to use the correct subject line and filename.
Always send yourself a copy of each e-mail message you send to me, and check immediately to see if you receive the message intact. You are responsible for sending e-mail correctly.

Here is the list of things you have to turn in:

At the start of class on the first due date, place the following item on the "counter" in front of me:
- a hardcopy of your level 2 (or greater) program. (All the source code, i.e. all the *.h and *.cpp files) Make sure all the code is properly formatted and that it all shows on the paper.
Using the subject line: CS3100,prog2.2 send the following item to me by e-mail before midnight on the first due date:

One shell archive file (only one) containing items 1-4.
1. All source files for your level 2 program (everything I will need to compile and run it: all *.cpp files and *.h files, including Queue code)
2. Your test script showing adequate testing of your level 2 program.
3. A file named 'README' containing the compilation command one should use to compile your program.
4. A copy of your 'makefile' if you used one.
At the start of class on the second due date, place the following item on the "counter" in front of me:
- a hardcopy of your final level program. (all the source code) Make sure all the code is properly formatted and that it all shows on the paper.
Using the subject line: CS3100,prog2.f send the following item to me by e-mail before midnight on the second due date:

One shell archive file (only one) containing items 1-4.
1. All source files for your final level program (everything I will need to compile and run it: all *.cpp files and *.h files, including Queue code)
2. Your test script showing adequate testing of your final level program.
3. A file named 'README' containing the compilation command one should use to compile your program.
4. A copy of your 'makefile' if you used one.

Note that there are no spaces in the subject lines given. It is important that you do not insert any spaces. My e-mail address is: john@ishi.csustan.edu.

DUE DATES:

For due dates, see the class schedule.