The University of Melbourne
School of Computing and Information
Systems
COMP10002 Foundations of Algorithms
Semester 1, 2025
Assignment 1: Exploring Spaces
Due: 11:59 pm Friday 02 May 2025
Version: 1.3
April 23, 2025
IMPORTANT NOTES:
• Please be aware that we have changed the submission location to be
on GRADESCOPE, instead of ED. You will need to submit one file
a1.c onto the grade-scope submission tab.
• Please note that the auto-grader on gradescope will provide sugges tions on your coding style that will contribute to the style mark.
• The expectations for Task 2 have been further clarified.
• For the bonus challenge we have made it count for 1 bonus mark
Please see the FAQ for instructions on how to submit the assignment.
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At some point in time you may have seen one of these... You have prob ably even encountered them in a variety of video games from Pac-man to
Animal Crossing...
Or maybe you have heard the myths of labyrinths with monsters hidden
in their depths...
This is because spatial exploration puzzles, like mazes are one of the old est form of playful activities we have.
We live a world where we are constantly physically exploring and nav igating with our bodies. So it’s almost a no-brainer that we would see
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this kind of activity show up in our play. Spatial exploration puzzles span
many different types of navigation problems, but for today we will focus
on one called pathfinding.
Pathfinding is the act of finding a possible path between two locations. Of ten we are looking for the shortest-path, but sometimes we may look for
other types of paths. In modern games, pathfinding is used to tell charac ters how to move through the world. When people are chasing you in the
Untitled Goose Game, or your Sim can’t get out of the pool because you
deleted the ladder, those are examples of path finding at work.
For this assessment, we are going to be putting our algorithmic thinking
to the test by exploring simple pathfinding.
About the Assignment
Assignment Structure
Like a game, this assignment is divided into levels with different tasks.
Like any good game, each subsequent level builds on the skills and tech niques you used in the previous level. We recommend trying them all in
order for this reason.
To help get you started, each level will outline the problem, your require ments for the level, any information about the problem space that may
be useful to you, and an example of output from one of the provided test
files. Occasionally we will also highlight helpful hints and tips in a blue
box like so:
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Hey! Listen!
This is an example of what a hint/tip will look like.
Bonus Challenge:
At the end of the assignment, there is a skill-testing bonus challenge.
The bonus challenge is a slightly more advanced problem that you
are invited to try. There are no extra marks associated with it.
Learning Outcomes
By completing this assessment you will demonstrate your understanding
of the following coding concepts:
• Input processing,
• Control structures (conditionals and loops),
• Functions, and
• Arrays.
You will also be demonstrating your algorithmic problem solving skills,
particularly showing how you understand searching problems and recur sion.
Getting Started
For this assignment, you will be given the following:
• a skeleton code file (a1.c) with a semi-complete main function, a set
of function prototypes for you to complete, and comment space for
your answers to written questions;
• a set of test input files for the various levels (test0.txt, test1.txt,
test2.txt); and,
• examples of correct outputs for the test files both in this document,
and as a set of files such as (test0-level1-out.txt, test0-level2-out.txt,
test0-level3-out.txt, test0-level4-out.txt) etc.
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Before you start coding, you need to get to know the structure of the game.
After reading this assignment and the FAQ at the end of this document,
spend time familiarizing yourself with (a1.c). Pay attention to the vari ables, constants, and function prototypes already in-place. These will be
useful hints at how to complete the functions later!
And remember, Algorithms are fun!
Level 1: Hello World? [4 marks]
In order to do any pathfinding, we need a representation of a “world” that
we can move around in. But how do we represent that on a computer?
There are a variety of ways, but for simplicity we can think of our world
like a map with a grid imposed on top of it. This way every location on
the map has an x and y coordinate that tells us where on the map it is.
We can extend this understanding to think about our map as a two-dimensional
array. Every element of this 2D array is the relevant structure at that (x,
y) point. For example, imagine a world where there are walls blocking
our path; the array could store a symbol of a wall at the real wall’s (x, y)
location to show us that it is there.
This leads us to our first task: create the map for our world!
Requirements
To successfully complete this level you must:
1. Complete the function FillMap() so it can read in the map data from
the test file;
Hey! Listen!
We are running your code using input redirection (using < in
commandline) to pass the test file to program so you can use
the standard input functions, like scanf! To have a closer look
at the command we are running, see the BUILD HELP.txt file in
the skeleton code folder we have provided.
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2. Complete a function called PrintMap() that prints out the map to the
terminal screen; and,
3. Save the starting and ending locations you found to the appropriate
variables in the main function.
Hey! Listen!
Think about how this task interacts with C scopes, and what
tools we have to manipulate variables in different scopes.
What we know about the problem
File structure. The input file will always contain at least 3 lines of data.
• Line 1:
– Two positive integers representing the row (y coordinate) and
column (x coordinate) of the STARTING position
• Line 2:
– Two positive integers representing the row (y coordinate) and
column (x coordinate) of the ENDING position
• Line 3:
– One positive integer representing the number of obstacles (i.e.
BLOCKS) on the map
Depending on the number of blocks, the input file will also have the coor dinates for those blocks.
Map size. To make the process easier, we have fixed the map size as a
square grid. The specific size value is defined as a preprocessor directive
using #define␣N at the top of the (a1.c) file. During graded testing this
number and the input we test on may change. So when creating your code,
make sure it can scale with the map size.
Location information. You can assume for this input that we will not
put the starting, ending, and/or blocks in the same location. This means
the start and end will not be the same place. This will be true for all tests.
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Sample Output
Your output for the Level given the same test file, should look like Fig. 1.
Figure 1: Example of expected output for Level 1 using test2.txt
Level 2: Na¨ıve Pathfinding [6 marks]
Great! Now we have our map rendered in the computer and know where
the starting and ending points!
We now want to start working towards finding our way from the starting
point to the exit point! Let’s start by taking a somewhat intuitive approach
we will call na¨ıve pathfinding.
In our na¨ıve pathfinding we will start moving in one direction (e.g. down
the rows) until we can’t move anymore or until we have reached the correct
row for the exit. If we ever reach a block, we will try to move one column
over towards the exit, and then continue moving down. Once we have
reached the correct row, we will then start moving columns towards the
exit using the same logic (going until we hit a block, then moving up or
down a row to compensate, before returning to the columns).
See requirements for a description of the algorithm below. Fig. 2 renders
what the map would look like after each step.
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Figure 2: Example of each step the path would take for Level 2 using
test2.txt
For your second task, you will need to implement the described function
and answer some questions about it.
Requirements
To successfully complete this level you must:
• Complete the function SimpleDirections() so it can both render a
path between the starting and ending space using +, and output the
number of steps needed to reach the end. The pathfinding must use
the following logic:
– From the starting point, the path will always try move along the
rows towards the row containing the end point,
– If the path hits a block, it will move left or right one column in
the direction towards the end point,
– The path will repeat the previous two steps until it reaches the
correct row.
– The path then repeats the above process for the columns (i.e.
moving along the columns until it encounters a block, and then
moving around the block through the rows)
– The path then begins to move across the columns in the direc tion of the end point.
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– If at any stage, you cannot make a move following the above
rules you must stop.
• Modify the skeleton code, so that in the case that you have no more
valid moves from the above algorithm, so that it now prints "SimpleDirections
took N steps and got stuck.\n\n", and then the map instead of
"SimpleDirections took N steps to find the goal.\n\n" and then
the map, where N is the number of steps taken before not having any
valid moves or reaching the end point.
• Answer the following questions in the comment section indicated at
the end of your a1.c file:
– List some cases where this process will not produce our ex pected results? Why is this?
Hey! Listen!
Think about how the assumptions we have to make about
the problem space (i.e. the map).
– Do you think this process will be efficient for bigger maps? Why,
or why not?
What we know about the problem
Assumptions about the map. At this point you can assume the follow ing information:
• There will always be at least one path that will take you from the
start to end. This may not always be the case in the future. We have
provided an example in Fig. 4 of the expected output.
• There is only one starting and one ending position. However, you
should consider that the starting and ending positions could be any where on the map grid.
Sample Output
Your output for the Level given the same test file, should look like Fig. 3
or Fig. 4.
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Figure 3: Example of output from Level 2 using test2.txt input.
Figure 4: Example of output from Level 2 using test3.txt input.
Level 3: Closest Neighbours [4 marks]
Hooray that’s one way to find a path to the end! Let’s try to come up with
another (slightly more generic) process!
Intuitively, we may want to start by finding a valid (i.e. unblocked, empty)
space adjacent to our starting space — i.e. its neighbour. If we then move
into that new valid space, we can repeat the search process by just looking
for the next adjacent empty space. In this way, we are not pre-emptively
deciding on the direction of our search, and so we do not need to give our
search an end point. We call this process Closest Neighbours.
Our third task, is to implement this Closest Neighbours algorithm as
discussed. Fig. 5 illustrates what the path looks like on the map at every
step of this Closest Neighbours algorithm.
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Figure 5: Example of each step the path would take for Level 3 using
test1.txt
Requirements
To successfully complete this level you must:
• Complete the function ClosestFreeNeighbour() to find a path from
a known starting position to an unknown ending position using the
following logic:
– Check if your neighbour is empty, and if yes then move to it
– We check the neighbours in the following order:
1. Above
2. Right
3. Down
4. Left
– We end the function once we find the ending position or there
is no available neighbour to move to.
What we know about the problem
Assumptions about neighbours. We know that any individual location
will have at most four (4) neighbours: above, right, down, and left. Based
on this we should be able to know where a neighbour is relative to our
current location.
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Structure of the process. We can see that this process requires complet ing the same process on a smaller version of the same problem. We can
leverage this to approach this problem using a particular technique that
we covered in lecture.
Hey! Listen!
Think about the Triangles and Tower of Hanoi example from lecture!
Assumptions about Map data. You can assume that the map is back to
its original state when you start this process. We have provided you with
a RefreshMap() function which wipes the map back to just its starting
configuration. We already call this for you between every Level() call in
the main function so that you do not have to worry about carrying over
data.
This function is not needed in the current iteration of the program that
runs each level with a seperate instance of the program, it does however
still exist within the program.
Sample Output
Your output for the Level given the same test file, should look like Fig. 6.
Figure 6: Example of output from Level 3 using test2.txt input.
Level 4: Finding a Complete Path [2 marks]
Awesome, now we have some way to find a path from a starting location
to an unknown ending point! But will this method always work?
Our final task is to theorize about how we could improve on our
Closest Neighbours approach.
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Requirements
To successfully complete this level you must answer the following ques tions in the comment section indicated at the end of your a1.c file:
• Do you think the Closest Neighbour process will always work? Why
or why not? Write out what you know about the problem space (i.e.
possible board setups) to support your thoughts about the process.
• How would you improve the Closest Neighbour process to handle
edge cases? Use pseudocode to describe your proposed algorithm.
Hey! Listen!
Think about how we could remember where we have been.
What we know about the problem.
For this final task, you should write out what you know about the prob lem space of mazes (generically). Thinking about what the problem space
looks like, is a very important skill in algorithmic thinking.
Sample Output
Your output for the Level is just text and pseudocode in a comment in your
assignment code file.
Bonus Challenge [1 bonus mark]
Note that in the test cases given this is described as taskN-level-4-out.txt
Bonus Challenge:
Now that you have proposed a way to improve on the Closest
Neighbours method, we need to try it out. In this Skill Testing
Challenge, you must try to implement the changes you suggested
in Level 4 so that you have a more robust maze solving algorithm!
Your implementation should mark all paths you visited/tried with
a * and the final resulting path with +.
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FAQ
Here are some frequently asked questions about submission and policies
for this assignment.
How do I submit the assignment?
You will need to submit your assignment on the EdStem Platform, as you
have used for the assessed problem sheets.
You will need to submit your assignment on the Canvas LMS using
Gradescope. You may write your code outside the Ed platform in a code
editor such as Visual Studio if you wish, but you will need to copy your
finalised code onto Ed to submit it. To submit your code, you will need to:
1. Log in to LMS subject site,
2. Navigate to “Assignment 1” in the “Assignments” page,
3. Click on “Load Assignment 1 in a new window”,
4. Follow the instructions on the Gradescope “Assignment 1” page,
5. Click on the “Submit” link to make a submission.
Deadline and Late Submissions
The deadline for this assignment is 11:59 pm Friday 02 May 2025. You can
submit as many times as you want to before this deadline. Only the last
submission made before the deadline will be marked. You can (and should) sub mit both early and often – to check that your program compiles correctly
on our test system, which may have some different characteristics to your
own machines.
Submissions made after the deadline will incur penalty marks at the rate of
-3 marks per day or part day late. Late submissions after 11:59 pm Tues day 06 May 2025 will not be accepted. Do not submit after the deadline
unless a late submission is intended.
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Special Considerations
Special 24-hour extension. If you need just a little more time to finish
your assignment, we are offering an automatically approved 24-hour ex tension to students who fill out this Automatic Extension Form. There
is no further documentation required, and you are guaranteed to be ap proved for this extension.
1-3 Day Extensions: For extensions between 1 to 3 working days, stu dents may complete the FEIT online declaration form. The Online Dec laration Form covers most written assessments, and must be submitted
before the assignment due date. The Online Declaration form does not
require any medical documentation from students at time of submission,
but this could be asked for at a later date. Extensions applied for through
the FEIT system are not automatically approved.
4+ Day Extension: If you need more than 3 working days, or alternative
considerations for an assignment, you will need to submit a request on the
Special Consideration Portal. The Special Consideration application will
require students to provide supporting documentation for their circum stance. The full application must be submitted within four working days
of the assessment due date; it can be submitted in advance of the due date
if you know you will be impacted. Special Consideration is not auto matically granted. They are assessed by Student and Scholarly Services
(SASS) and passed to FEIT if you are found eligible for consideration.
Academic Adjustment Plans: For those of you who have registered your
Academic Adjust Plan with our subject, please follow the details set out in
your plan regarding any considerations for deadlines, etc.
How will I be marked?
The assignment is out of 20 marks. The breakdown of marks in the assign ment is:
• Level 1 [4 marks]
• Level 2 [6 marks]
• Level 3 [4 marks]
• Level 4 [2 marks + 1 bonus mark]
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• Code Structure and Style [4 marks]
This assignment has both coding and written components. Below we have
outlined how they will be marked.
Marking your code
Overall your code will be marked on its functionality, structure, and style.
Details about the specifics for each Level is in the marking rubric. Here we
have a brief description of what we mean by functionality, structure, and
style.
Functionality. Your code’s functionality will be autograded by test cases.
Given the size of this class it is the only feasible way for us to mark your
work. Part of your code mark for each Level will be based on how many
of our test cases it passes.
IMPORTANT !
Since we are autograding your code, it MUST compile in order to
receive a grade. If your code does not compile, you will receive a 0
for the functionality portion of your work. Our markers will not be
spending any time troubleshooting it for you during marking.
Code Structure. Part of your code mark will be based on the structure of
your actual code. The marker will take a quick look at the functions you
have created to determine if you are using the appropriate techniques for
the problem.
Code Style. Your code style is important to develop as it makes your
code easier to read and debug. To this end 4 marks in the assignment
is reserved for evaluating your consistency with coding style and good
practice behaviours. We are particularly looking for some of the following:
• Appropriate code commenting,
• Consistent and reasonable naming conventions for functions and vari ables,
• Consistent indentation, bracket placement, whitespace, short lines,
and other code readability elements like authorship comment,
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• Appropriate use of maintenance and abstraction tools for efficient
code design (e.g. #define variables, functions use to reuse code)
This list is not comprehensive, and “appropriateness” is up to interpreta tion by assignment marker based on a holistic look at your code.
To help you develop good style, we suggest taking a look at some of the
following style guides:
• CS50 Style Guide,
• Google’s Style Guide (Written for C++),
• Linux Kernal Coding Style Guide
You do not have to follow any of these guides specifically, but note their
similarities when you are developing your own coding style.
Marking written answers
The goal of the written questions is to make you think critically about the
code you just wrote, and whether it is a robust solution to the problem.
As such, we are more concerned with seeing that you have genuinely at tempted to think about the problem than having a singular correct answer.
To reflect this, written answers are marked based on both the correctness
and quality of an attempt. This means a genuine attempt, even if the result
is wrong will still earn you some mark so we encourage you to really try.
A good answer attempt should:
• Incorporate the terminology and language from the course;
• When appropriate, refer to the algorithms and concepts you are fa miliar with from the course (e.g. does your approach look like any
other problem solving techniques?)
Working with Friends and Academic Integrity
Learning is an uncomfortable process of going from not knowing some thing to knowing something. So while our assignments are designed to
be achievable, they can also be challenging because they are asking you
to demonstrate that learning in an active way. This means there are going
to be times in the learning process where you are struggling. We aim to
support you with our lectures, workshops and the First Year Centre. But
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another important form of support are your peers in the class with you!
It is really helpful to have people around you who are also working to wards learning the same material. We strongly encourage you to discuss
your work with others, but what gets typed into your program must be
individual work, not from anyone else. If you are copying solutions from
a friend or the internet, you lose out on the chance to do the real learning
that will help you throughout this subject and beyond.
We know it is hard to watch our friends struggle, especially when we see
how much effort they are putting into their work. However, giving them
your code removes their opportunity to learn and grow. The best way to
help your friends in this regard is to say a very firm “no” when they ask for
a copy of, or to see, your program. Feel free to discuss concepts with them,
and direct them to one of the other subject supports like their workshop
tutors, the First Year Centre, the PASS program, ED Discussion boards, or
the professors. We truly want you all to succeed, and are willing to put in
the time and effort to help anyone struggling at any stage of the learning
process.
So please, do not give (hard or soft) copies of your work to anyone else; do
not “lend” your memory stick to others; and do not ask others to give you
their programs “just so that I can take a look and get some ideas, I won’t
copy, honest”.
A sophisticated program that undertakes deep structural analysis of C code iden tifying regions of similarity will be run over all submissions in “compare every
pair” mode. See https://academichonesty.unimelb.edu.au for more in formation.
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