CS 411 Fall 2025 > Assignment 6 (Huffman Codes)

CS 411 Fall 2025
Assignment 6 (Huffman Codes)

Assignment 6 is due at 5 pm Tuesday, November 25. It is worth 85 points.

Procedures

This is, optionally, a group assignment. You may work in a group of two, if you wish. Each group only needs to turn in a single copy of the assignment. Under normal circumstances, each group member will receive the same grade on the assignment.

Turn in your answer to the exercise below on the UA Canvas site, under Assignment 6 for this class.

Your submission must consist of the source code for Exercise A (files huffcode.hpp and huffcode.cpp).
I may not look at your homework submission immediately. If you have questions, e-mail me.

If you work in a group:

The assignment files must contain the names of both group members.
One student submits the assignment as usual, on Canvas.
The other student submits an empty assignment (no attached source or header files) on Canvas, with a note indicating whom the assignment was done with.

Exercises (A only, 85 pts total)

Exercise A — Huffman Codes

Purpose

In this exercise, you will implement Huffman coding. Given character weights, your package will be able to construct a Huffman code, which it can then use to encode and decode strings.

Instructions

Write a class HuffCode, defined in files huffcode.hpp and huffcode.cpp.

Class HuffCode should include the following public member functions.

Default constructor, copy constructor, copy assignment, destructor. All of these should do the usual things.
- So you can use the compiled-generated versions, as long as you do not do anything silly like declaring a data member that is a pointer.
Member function setWeights, prototyped as follows (remember, this and later functions are all class members):
[C++]
```
void setWeights(const std::unordered_map<char, int> & theweights);
```
Function setWeights sets the character weights. It is given an unordered_map, as above; the value corresponding to a character is its weight. Characters whose weight is not specified will not occur in any texts to be encoded.
Member function encode, prototyped as follows:
[C++]
```
std::string encode(const std::string & text) const;
```
Given a string of characters, each of which has already had its weight defined (using setWeights), this returns a string of zero ('0') and one ('1') characters, representing the given text, encoded using an appropritate Huffman code. See Examples, below, for an example.
Member function decode, prototyped as follows:
```
std::string decode(const std::string & codestr) const;
```
Given a string of zero ('0') and one ('1') characters, encoded using the Huffman code generated by the class, this returns the corresponding text. In particular, if the return value of encode is passed to this function, then it will return the argument that was passed to encode. See Examples, below, for an example.

Your code may generate and use any Huffman code that is correct for the given weights.

Examples

[C++]

HuffCode h;

std::unordered_map<char, int> w;
w['a'] = 1;
w['b'] = 2;
w['c'] = 3;
h.setWeights(w);

// I will assume the code is
//   a: 00
//   b: 01
//   c: 1
// There are other possible Huffman codes for the above weights;
//  these would result in different behavior below.

std::cout << h.encode("aca") << std::endl;
// Above prints "00100"

std::cout << h.decode("00100") << std::endl;
// Above prints "aca"

std::cout << h.decode("01000111") << std::endl;
// Above prints "babcc"

Skeleton Files

I have provided unfinished “skeleton” files huffcode.hpp and huffcode.cpp, in the ZIP file huffcode.zip. You may use these as the basis for your own work, if you wish.

Test Program

A test program is available: huffcode_test.cpp. If you compile and run this program (unmodified!) with your code, then it will test whether your code works properly.

Do not turn in the test program.

Notes

Coding standards are as for Assignment 2.
Your code may be tested with additional input beyond that given in the posted test programs.

CS 411 Fall 2025 Assignment 6 (Huffman Codes)