COMP9024 20T2 Data Structures and Algorithms

Change Log

We may make minor changes to the spec to address/clarify some outstanding issues. These may require minimal changes in your design/code, if at all. Students are strongly encouraged to check the change log regularly.

Version 1: Released on 10 July 2020

Objectives

The assignment aims to give you more independent, self-directed practice with

  • advanced data structures, especially graphs
  • graph algorithms
  • asymptotic runtime analysis

Admin

Marks 3 marks for stage 1 (correctness)
5 marks for stage 2 (correctness)
2 marks for stage 3 (correctness)
1 marks for complexity analysis
1 mark for style
———————
Total: 12 marks
Due 11:00:00am on Monday 3 August (week 10)
Late 2 marks (16.67%) off the ceiling per day late
(e.g. if you are 25 hours late, your maximum possible mark is 8)

Aim

Your task is to write a program goNSW.c for finding an optimal public transport connection that takes into account a given departure time and user preferences.

Input

Network

Your program should start by prompting the user to input a positive number n followed by n lines, each containing the name of a train station or bus/light rail stop. An example is: 

./goNSW Enter the total number of stops on the network: 5 Chinatown
Central
Kensington
UNSW
Wynyard

You may assume that:

  • The input is syntactically correct.
  • Names require no more than 31 characters and will not use any spaces.
  • No stop name will be input more than once.

Hint:

To read a single line with a stop name you may use: 

scanf("%s", stop);   // stop is a character array (= string variable)

Schedules

Next, your program should ask the user for the number m of busses, trains and light rail vehicles running during a day, followed by m schedules. Each schedule requires the number of stops, k≥2, followed by k*2 lines of the form: 

hhmm
stop-name
meaning that passengers can get on or off at that time (hh – hour, mm – minute) at that stop. An example is: 
Enter the number of schedules: 2 Enter the number of stops: 5 1640
UNSW
1645
Kensington
1705
Central
1708
Chinatown
1715
Wynyard Enter the number of stops: 2 1645
UNSW
1700
Central

You may assume that:

  • The input is syntactically correct: 4 digits, then a new line with the name of a stop.
  • All times are valid and range from 0000 to 2359.
  • Stops are input in the right (temporal) order.
  • There are no overnight connections: Each bus, light rail or train will reach its final stop before midnight.
  • Only valid stops that have been input before will be used.

Queries

After reading the transportation network, your program should prompt the user to search for a connection: 

From: UNSW To: Wynyard Depart at: 1630

Again you may assume that the input is correct:

  • Only stops that have been entered before are used and a valid time is given.
  • The two stops will not be the same.

If the user inputs "done," then your program should terminate: 

From: done Thank you for using goNSW.

Stage 1 (3 marks)

For stage 1, you should demonstrate that you can read the input and generate a suitable data structure.

For this stage, all test cases will only use queries (From, To, DepartAt) for which

  • there is only one bus, train or light rail service connecting  From  and  To ; and
  • this is guaranteed to depart on, or after, the requested time,  DepartAt .

Hence, all you need to do for this stage is find and output this direct connection, including all stops along the way and the arrival/departure times. Here is an example to show the desired behaviour of your program for a stage 1 test: 

./goNSW Enter the total number of stops on the network: 7 Wynyard
QVB
Central
Kensington
UNSW
Glebe
Broadway Enter the number of schedules: 2 Enter the number of stops: 5 0945
Wynyard
0950
QVB
1000
Central
1022
Kensington
1027
UNSW Enter the number of stops: 2 1459
Broadway
1518
Glebe From: Broadway To: Glebe Depart at: 0950 1459 Broadway
1518 Glebe

From: QVB To: Kensington Depart at: 0950 0950 QVB
1000 Central
1022 Kensington

From: done Thank you for using goNSW.

Stage 2 (5 marks)

For stage 2, you should extend your program for stage 1 such that it always finds, and outputs, a connection between  From  and  To  that

  • departs on, or after, the requested time  DepartAt ; and
  • arrives as early as possible.

You should assume that:

  • Changing takes no time: Passengers arriving at a stop can get onto any other train, bus or light rail service that leaves that stop at the same time or later.
  • In all test scenarios there will be at most one connection that satisfies all requirements.

If there is no connection, the output should be: 

No connection found.

Here is an example to show the desired behaviour and output of your program for a stage 2 test: 
./goNSW Enter the total number of stops on the network: 5 Central
Eastwood
Redfern
Strathfield
Wynyard Enter the number of schedules: 2 Enter the number of stops: 4 0915
Eastwood
0935
Strathfield
1002
Redfern
1017
Wynyard Enter the number of stops: 3 1005
Redfern
1010
Central
1015
Wynyard From: Eastwood To: Wynyard Depart at: 0910 0915 Eastwood
0935 Strathfield
1002 Redfern
Change at Redfern
1005 Redfern
1010 Central
1015 Wynyard

From: Eastwood To: Redfern Depart at: 0920 No connection found.

From: done Thank you for using goNSW.

Stage 3 (2 marks)

For stage 3, you should extend your program for stage 2 such that:

If there are two or more valid connections with the same earliest arrival time, choose the one with the latest departure time.
Here is an example to show the desired behaviour and output of your program for a stage 3 test: 
./goNSW Enter the total number of stops on the network: 5 Chinatown
Central
Kensington
UNSW
Wynyard Enter the number of schedules: 2 Enter the number of stops: 5 1640
UNSW
1645
Kensington
1705
Central
1708
Chinatown
1715
Wynyard Enter the number of stops: 2 1645
UNSW
1700
Central From: UNSW To: Wynyard Depart at: 1630 1645 UNSW
1700 Central
Change at Central
1705 Central
1708 Chinatown
1715 Wynyard

From: done Thank you for using goNSW.

Complexity Analysis (1 mark)

Your program should include a time complexity analysis for the worst-case asymptotic running time of your program, in Big-Oh notation, depending on the size of the input:

  1. the number of stops, n
  2. the number of schedules, m
  3. the maximum number k of stops on a single train, bus or light rail line.

Hints

If you find any of the following ADTs from the lectures useful, then you can, and indeed are encouraged to, use them with your program:

You are free to modify any of the six ADTs for the purpose of the assignment (but without changing the file names). If your program is using one or more of these ADTs, you should submit both the header and implementation file, even if you have not changed them.

Your main program file goNSW.c should start with a comment: /* … */ that contains the time complexity of your program in Big-Oh notation, together with a short explanation.

Testing

We have created a script that can automatically test your program. To run this test you can execute the dryrun program that corresponds to this assignment. It expects to find, in the current directory, the program goNSW.c and any of the admissible ADTs (Graph,WGraph,stack,queue,PQueue,list) that your program is using, even if you use them unchanged. You can use dryrun as follows: 

9024 dryrun goNSW

Please note: Passing dryrun does not guarantee that your program is correct. You should thoroughly test your program with your own test cases.

Submit

For this project you will need to submit a file named goNSW.c and, optionally, any of the ADTs named Graph,WGraph,stack,queue,PQueue,list that your program is using, even if you have not changed them. You can either submit through WebCMS3 or use a command line. For example, if your program uses the Graph ADT and the queue ADT, then you should submit: 
give cs9024 assn goNSW.c Graph.h Graph.c queue.h queue.c

Do not forget to add the time complexity to your main source code file goNSW.c.

You can submit as many times as you like — later submissions will overwrite earlier ones. You can check that your submission has been received on WebCMS3 or by using the following command: 
9024 classrun -check assn

Marking

This project will be marked on functionality in the first instance, so it is very important that the output of your program be exactly correct as shown in the examples above. Submissions which score very low on the automarking will be looked at by a human and may receive a few marks, provided the code is well-structured and commented.

Programs that generate compilation errors will receive a very low mark, no matter what other virtues they may have. In general, a program that attempts a substantial part of the job and does that part correctly will receive more marks than one attempting to do the entire job but with many errors.

Style considerations include:

  • Readability
  • Structured programming
  • Good commenting

Plagiarism

Group submissions will not be allowed. Your program must be entirely your own work. Plagiarism detection software will be used to compare all submissions pairwise (including submissions for similar projects in previous years, if applicable) and serious penalties will be applied, including an entry on UNSW's plagiarism register.

  • Do not copy ideas or code from others
  • Do not use a publicly accessible repository or allow anyone to see your code, not even after the deadline

Please refer to the on-line sources to help you understand what plagiarism is and how it is dealt with at UNSW:

Help

See FAQ for some additional hints.

Finally …

Have fun! Michael

Reproducing, publishing, posting, distributing or translating this assignment is an infringement of copyright and will be referred to UNSW Conduct and Integrity for action.

2020-07-27