COMP2230/COMP6230 Algorithms

The University of Newcastle, Australia
School of Information and Physical Sciences
COMP2230/COMP6230 Algorithms
Assignment 1 Marks 100 Weight 15%
Individual Submission via Canvas
1 Learning Outcomes
This assignment will require students to:
1. Apply specific search algorithms studied in the course to unfamiliar problems.
2. Select appropriate data structures to optimize the performance of the algorithms.
3. Use algorithm analysis techniques to determine the asymptotic complexity of algorithms.
2 General Instructions
1. Programming Language: All students are required to use the Java programming lan
guage for this assignment. You may only use in-built Java library methods and classes (that
are listed in the documentation for the Java Standard Edition API), as well as ones you write
yourself. You are not permitted to import any third-party libraries to use in this assignment.
2. Individual Assignment: Each student must complete the main tasks specified as an indi
vidual to demonstrate achievement of the learning outcomes; no collaboration is permitted.
3. Marking Guideline: Marks are provided for functionality and for efficiency (optimising the
time complexity of your algorithms). The purpose of these tasks is three-fold: (i) you need to
problem-solve: figure out how best to solve each task, (ii) implement and test the solution, and
(iii) determine the complexity of the algorithms used in solving the problems.
4. Academic Integrity: Each student must complete the tasks in this section individually, no
collaboration with other students is permitted. All code must be your own original work. The
use of generative AI tools, including but not limited to: ChatGPT, Copilot, Tabnine, OpenAI
Codec, etc, is NOT permitted. Any collaboration with other students, or use of generative
AI will be considered a breach of the Academic Integrity Policy and may be referred to the
Student Academic Conduct Officer (SACO) for disciplinary action.
3 Getting Started
Download the package assignment1base.zip from Canvas. In this package you will find three files:
1. TrafficAssistant.jar: A pre-compiled Java file that contains two classes: MapGenerator and
TrafficCheck. These classes are black-boxes, you do not need to know how they work.
• When compiling, you will need to ensure this jar file is on the Java classpath. You can
use the -cp flag when invoking the Java compiler to set the classpath.
• This file was compiled with Java 21. To run it, you will need to use version 21 or higher.
2. TrafficAnalyser.java: This is where you will complete your assignment, some starting code
has been provided to allow compilation.
3. TrafficMain.java This is the main class to control the program, calling your methods from
TrafficAnalyser.java. You may modify this file underneath the marked comment in order
to test your code, but the modifications will not be really not part of the assignment.
14 Problem Scenario
In the bustling metropolis of Veridian City, chaos reigns during rush hour. The streets overflow with
vehicles, commuters jostling for space, and traffic signals blinking in desperate confusion. The city
council has had enough. They have turned to you, a brilliant second-year algorithms student—to
untangle this vehicular web. Your mission is to step into the role of one of the city’s digital traffic
engineers, analyse vast streams of traffic data, identify bottlenecks, optimize signal timings, and
propose innovative solutions. The city’s future hangs in the balance, and every algorithm you design
could mean smoother commutes, reduced emissions, and happier citizens.
Figure 1 shows an example of a roadmap of a city like the Veridian city. In fact it is the test map
given in TrafficMain.java in the base code supplied to you. Note that in every run of your
program, a map generated randomly by the MapGenerator class will be used.
South
Junction
North
Crossing
Eastern
Plaza
Western
Metro
Tall
Towers
Simple
Shops
Interesting
Intersection
Central
Station
Tiny
Train
yard
Perfect
Park
Big
Bould
vard
Inner City Intersections
Interesting Intersection,
Simple Shops, Tall Towers,
Perfect Park, Central Station,
Tiny Trainyard, Big Boulvard
Bottleneck Roads
Pink Road, Purple Street,
Mauve Road
Slower Roads in
the Inner City
2 Roads with Speed > 7
Violet Road, Magenta Avenue
Figure 1: Veridian City Road Map
5 Problem Tasks
There are 4 tasks in this assignment. You have to complete all of the tasks to get total 100 marks.
5.1 Divided City (25 Marks)
In Veridian City, the rapid urban expansion has led to a chaotic network of roads. Multiple construc
tion companies have been building roads independently, leading to a disjointed city layout. Some
residents have even reported that they are unable to reach the ‘inner city’ from their suburbs due
to the lack of connected roads. For example, see the ‘inner city’ intersections in Figure 1. Your first
task is to analyse the city’s road network and determine the extent of this problem.
2
Blue Street,4
Magenta Avenue,9
Green Street,6
Cyan Road,7
Yellow
Street, 9
Violet Road,8
Red Street,2
Purple
Street,4
Pink
Road,3
Indigo
Road,1
Mauve
Road,2
Orange Street,2
Lime Avenue,4
Gold Avenue,65.1.1 City Mapping (15 Marks)
Take the list of roads built by various construction companies in Veridian City, and create some order
out of the chaos in preparation for future processing.
• Write the method void loadMap(). The first few lines in this method are written for you. It
will call the city registry to get a complete list of roads in the city.
• This list will be a serialized string in the following format:
"{{road1}, {road2}, {road3}, ... {roadN}}".
• Each road will be in the following format. The endpoints in the format are the intersection
names and the travel times for the roards are in minutes.
"{road-name, first-endpoint, second-endpoint, average-travel-time}"
• For example, a city with three roads might look like this:
"{{Alpha Road, Alpha/King Lights, Alpha/Park Crossing, 3.5},
{King Street, King/Park Roundabout, Alpha/King Lights, 4},
{Park Close, Alpha/Park Crossing, King/Park Roundabout, 8.2}}"
• This method has no return value, but you may assume for marking purposes that it will be
called first, before any other methods.
• Note the following information regarding the road list:
– For convenience, the intersections where roads meet are named after the most prominent
point of interest at that intersection.
– You will not receive conflicting or erroneous information, that is, road names will not be
repeated on the list provided, travel times will not be negative numbers, etc; so error
checking is not required.
– The number of roads is randomised, as are the road names, intersection names, and order
of the roads. To help with testing, a seed value has been exposed in TrafficMain.java
that will be passed to the map generator. By setting the same seed value, you will be able
to generate the same map across multiple runs.
– Veridian City currently has no one-way roads, though this may change in the future. If a
road exists, it may be travelled in both directions.
• Hint: This method is arguably the most important method in the program. The way you
setup the data structures here will affect the performance of all other methods in the program.
Notice that the street and intersection names are all strings but strings are usually not suitable
for a graph representation. So you should think of mapping the strings to integers. There could
be indexes for the intersections and/or streets. You may consider storing the strings in a list
and then use the indexes. You will then need to get the string from an index or vice versa. To
find the index for a string, you may perform some search: linear, binary, interpolation, or hash
table search. To find the string for an index, usually an array is useful. Carefully design these.
5.1.2 Critical Disconnection (10 Marks)
Some residents of Veridian City have been complaining that they cannot reach the ‘inner city’
from their homes. For example, in Figure 1, we cannot go to the inner-city intersections from
South Junction, North Crossing, Western Metro, or Eastern Plaza. You will need to determine
the extent of this problem to aid in planning future road construction.
3• The ‘inner city’ is defined as follows: If there are any intersections that cannot be reached
from other intersections, then it is possible to group intersections, where every intersection in
a group can reach any other intersection in the same group through a series of roads. Given
this, the ‘inner city’ shall be defined as the largest such group of intersections.
• Write boolean isInInnerCity(String intersectionName) method. The input will be the
name of an intersection in the city, and you must determine whether that intersection is a part
of the ‘inner city’. The answer will be a boolean value: true if the provided intersection is a
part of the largest group, and false if it is not. Use the disjoint sets to solve this problem.
• Hint: Two nodes are in the same set if they can be reached from one another. Consider union
with ranks and find with path compression for performance improvement.
5.2 Tangled Web (25 Marks)
In the heart of Veridian City, the roads weave a complex web of connections. As a digital traffic
engineer, you must navigate this maze, identify slower roads, and untangle busier intersections.
5.2.1 Go, Slow, Stop (10 Marks)
The city’s traffic problem is exacerbated by roads that are notorious for their slow travel times.
Identifying these roads is crucial for future traffic improvement plans. In Figure 1, see the slower
roads in the inner city with the speeds larger than a given threshold.
• Write the method int countInnerCitySlowRoads(double threshold). The input will be a
threshold that will be a positive rational number, and you must return the number of roads in
the ‘inner city’ with average travel times that are strictly worse than this threshold.
• Hint: At first glance, you may think to check every road. With some clever thought, and the
right data structures setup while loading the map, you may be able to solve this one much
faster, with the full efficiency bonus scored if you can achieve O(ln n).
5.2.2 Uncorking the Bottle (15 Marks)
Some roads in the city act as bottlenecks, disrupting the smooth flow of traffic. Identifying these
roads will help in planning road expansions or redesigns. See the examples of bottleneck roads in
Figure 1. Note bottleneck roads could be in the entire city, not just in the ‘inner city’.
• Write the method String[] cityBottleneckRoads(). This method needs to return an array
of road names in the ‘inner city’ such that, if any single road in the array were to be closed,
one or more intersections in the ‘inner city’ would no longer be part of that group. That is,
removing one of the roads in the array would disconnect one or more intersections in the ‘inner
city’. Your solution must use an iterative depth-first approach.
• Hint: There are pseudocode of various algorithms in the lecture slides and also many example
programs on the Canvas site. Consider carefully which one would be the most appropriate base
algorithm, and then modify it to suit the task.
5.3 Ministerial Visit (30 Marks)
The Minister for Transport is coming to visit Veridian City. However, the visit comes with its own
set of challenges. As the city’s digial traffic engineer, you have to address them.
45.3.1 The Minister’s Speech (12 Marks)
The minister will be giving a speech at a certain intersection in the city. Ensuring the Minister’s
safety during the speech is paramount, and the security services have asked for your help in this task.
Consider the road map in Figure 2. If the minister will be speaking at the intersection marked, and
the number of hops is set to 1, then the roads with a red line across them would need to be closed.
W
E
N
S
Airport
River
School
Housing
Housing
Supermarket
Hospital
Park
Fuel
Council
Stadium
Jungle
Farm
•
Minister’s
Speech
Figure 2: For the minister’s speech, lock down each intersection within the number of hops 1
• Write the method String[] lockdownIntersection(String intersectionName, int hops).
This method takes in the name of the intersection where the minister will be giving the speech
from, and a number of hops to define the area for lockdown. The method then returns an array
of roads that need to be closed during the minister’s speech to prevent anyone from accessing an
intersection from which the intersection the minister will be speaking from could be reached by
traveling a number of roads less than or equal to the number of hops provided. Your solution
must use an iterative breadth-first approach.
• Hint: There are pseudocode of various algorithms in the lecture slides and also many example
programs on the Canvas site. Consider carefully which one would be the most appropriate base
algorithm, and then modify it to suit the task.
5.3.2 I protest! (18 Marks)
We have an emergency! The city’s traffic problems have led to protests during the minister’s visit.
Your task is to create the best action plan to contain the protests by closing roads within the city.
Consider the road map in Figure 3. The protests initially start at the three intersections marked.
However, we will consider two groups of protests here. The two north-most protests are considered
the same group as they are connected by a single unclosed road. The south protest is not connected
5to another other protest by a single unclosed road. We see that the northern protest group can
spread to four more intersections while the southern group can spread to three intersections. As
4 > 3, we will choose to isolate the northern group first by closing the four roads marked.
W
E
N
S
Airport
River
School
Housing
Housing
Supermarket
Hospital
Park
Fuel
Council
Stadium
Jungle
Farm
•
•
•
Protest
Protest
Protest
Figure 3: For the minister’s speech, lock down an intersection with the number of hops 1
Following the above road closure, the norther group is completely closed now, but the southern
group can move. The protest will spread to the three adjacent intersections but stay as one group
and the only group at this stage. To contain this group completely, we will need to close five roads.
See Figure 4 to see the example after the second round of road closure. With all protests closed from
spreading further, we finish by closing the total number of nine roads.
• Write the method int containProtests(String[] intersectionNames). This method takes
in an array of intersections where protesters are initially gathered, and must return the mini
mum number of roads that need to be closed to contain the spread of the protests.
• As you see from the above example, the process runs as a simulation, where, on each time step,
the city performs a road closure action, then the protests spread by one step. On the city’s
turn, roads should be closed around a single connected group of intersections with protesters
that will spread to the largest number of intersections on their turn (ties may be broken by
selecting the group that will spread the protest down the fewest number of roads). On the
protests turn, they will spread down any adjacent non-closed roads to connected intersections.
The protests will only travel a single ‘hop’ on their turn, then the city may act again.
• Hint: This problem seems very complex, but once the simulation steps are understood, the
implementation is quite straight-forward. At least, it is if you have the right data structures. . .
Start by breaking down the problem, the implementation should involve these steps: 1. Find
6W
E
N
S
Airport
River
School
Housing
Housing
Supermarket
Hospital
Park
Fuel
Council
Stadium
Jungle
Farm
•
Protest
•
Protest
•
Protest
•
Protest
•
Protest
•
Protest
Figure 4: For the minister’s speech, lock down an intersection with the number of hops 1
all ‘protest regions’ (connected intersections with protesters – note that two intersections are
not connected if the road between them is closed), additionally for each region keep track of
its frontier (neighbouring peaceful intersections the protest would spread to on the next step),
and the outbound roads of that frontier. 2. Isolate the most dangerous region (the one that
would spread to the most peaceful intersections on the next step), adding its outbound roads to
the answer and closing them for the next step. 3. Spread the protest in the remaining regions
outward by one non-closed road (this may result in two or more protest regions reaching each
other and becoming a single connected protest region, you will need to perform a merge if this
happens). For each step, consider what would be the best algorithm to use, and whether one or
more of the search algorithms discussed in class would be helpful for structuring the simulation.
5.4 Part 4: Report (20 marks)
Your solution should be accompanied by a short report. This report should explain how you have
implemented each algorithm, and demonstrate the time complexity for each one. You must prove
the time complexity stated in your report.
6 Submission
The deliverable for this assignment is a zip file named A1cxxxxxxx (where xxxxxxx is your student
number). This zip file should contain only the following files:
• TrafficAnalyser.java: This file should contain your solutions to each task, implemented
according to the specifications provided
7• readme.txt: Contains your name and student number, along with any special notes about
running your program for marking.
• report.pdf: A short report containing your analysis of each algorithm, including time com
plexity for your implementations with proofs.
• AssessmentCoverSheet.pdf: A completed Assessment Item Cover Sheet using the pdf found
from the link below. If the cover sheet is not included, your assignment cannot be marked.
https://www.newcastle.edu.au/__data/assets/pdf_file/0008/75383/AssessmentItemCoverSheet.pdf
You do not need to include the file TrafficMain.java as this will be replaced with a fresh copy
before marking. For this reason, while you modified TrafficMain.java to assist with development
and debugging, for marking, your program MUST run with the original version of this file. Notice
that a sample map with test cases has been provided in TrafficMain.java to help you get started.
Each test case shows the input and expected output of the corresponding method.
7 Marking Criteria
Total: 100 marks
7.1 Task 1: 25 marks
1. loadMap: 15 marks
• Correctly stores road layout into one or more data structures [10 marks]
• Efficient data structure(s) used [5 marks]
2. isInInnerCity: 10 marks
• Correct implementation to identify intersections not in ‘inner city’ [6 marks]
• Efficient implementation in time complexity [4 marks]
7.2 Task 2: 25 marks
1. countInnerCitySlowRoads: 10 marks
• Correct implementation to count roads in the ‘inner city’ with a travel time greater than
the threshold provided [7 marks]
• Efficient implementation in time complexity [3 marks]
2. cityBottleneckRoads: 15 marks
• Correct implementation using depth-first search from generic algorithm to find and return
roads that would disconnect the ‘inner city’ if removed [10 marks]
• Efficient implementation in time complexity [5 marks]
7.3 Task 3: 30 marks
1. lockdownIntersection: 12 marks
• Correct implementation of breadth-first search from generic algorithm returning correct
solution [8 marks]
• Efficient implementation in time complexity [4 marks]
82. containProtests: 18 marks
• Correct simulation of spreading protests, calculates correct number of roads to close [12
marks]
• Efficient calculation in time complexity [6 marks]
7.4 Report: 20 marks
1. Correct time complexity given for each algorithm matching code provided [10 marks]
2. Providing correct proofs and explanation [10 marks]
7.5 Mark Deductions
• Does not compile: Mark capped at 50%.
• Code quality – readability, indentation, header comments, method comments, inline comments:
Up to −20 marks.
• Instructions not followed (wrong class name, missing readme, something other than a zip
submitted, etc): Up to −20 marks
• Late submission: -10% per day
END OF ASSIGNMENT