2810ICT Ladder Gram

Assignment Description

The assignment requires a Python program to be completed that demonstrates understanding of the scripting languages taught in the course. As part of completing the program, existing functionality will need to be tested to ensure it is working correctly and new functions will be added to the program. A version control system shall be used to build the project and create and manage changes to source code over time.

Problem Statement

The goal of a ladder-gram is to transform a source word into the target word in the least number of steps. During each step, you must replace one letter in the previous word so that a new word is formed, but without changing the positions of the other letters. All words must exist in the supplied dictionary (dictionary.txt). For example, we can achieve the alchemist's dream of changing lead to gold in 3 steps (lead->load->goad->gold), or hide to seek in 6 steps (hide->side->site->sits->sies->sees->seek).

You have been supplied with a Python program (word_ladder.py) for this problem that was written by an obviously brilliant Python programmer who unfortunately did not believe in documentation nor that users would make any mistakes. Even worse, this code has been modified by a somewhat less talented programmer and it no longer works as efficiently as it used to.

Your assignment is to:

Produce a software design document based on the sample template for this program. In particular you must document each function within the program stating clearly what they do and how they do it.

You must modify the Python code so that:

• ALL possible user input errors are handled correctly.
• The program performs as it did before the less talented programmer got his hands on it. In particular it must go from lead to gold in 3 steps and hide to seek in 6 steps.

You must use the Python unittest module to test the functions of your program and provide test cases for each function. Note that to facilitate the testing, you can rewrite the code to make it testable.

You must make all program changes using a configuration management tool (BitBucket recommended) such that each change can be tracked and easily undone. For full marks, you must add the following functionality to the program:

• The user can supply a list of words that are not allowed to be used within the steps from a start word to a target word.
• The user has the option of asking for the shortest path from a start word to a target word.
• For 7810ICT students: The user has the option of asking for a list of all possible unique paths (i.e. no common words) of a certain length from the start word to the target word.