COMP2113 Programming Technologies / ENGG1340 Computer Programming II
Assignment 1
Deadline: 20 October 2022 (Thursday) 23:59


If you have any questions, please post to the Moodle discussion forum on Assignment 1.

Total marks: 100 marks
• 5 marks for proper code comments and indentation
• 95 marks for program correctness
A maximum of 5 marks will be deducted if you fail to follow the submission instructions strictly.



General Instructions

Read the instructions in this document carefully.

In this assignment you will solve 4 tasks and a tester would automatically test your submitted program. So if
your submitted files and program outputs do not conform to our instructions given here, your programs cannot
be evaluated and you will risk losing marks totally.

Sample test cases are provided with each task in this document. Note that the test cases may or may not cover
all boundary cases for the problem. It is also part of the assessment whether you are able to design proper test
cases to verify the correctness of your program. We will also use additional test cases when marking your
assignment submission.


Input and output format

Your C++ programs should read from the standard input. Also, your answer should be printed through
the standard output. If you failed to follow this guide, the tester may not able to give a score for your program.
Additionally, you should strictly follow the sample output format (including space, line breaker, etc.), otherwise,
your answer might be considered as wrong.



How to use the sample test cases for problems 3 and 4?
Sample test cases in text file formats are made available for you to check against your work. Here's how you
may use the sample test cases. Take Question 4 test case 3 as an example. The sample input and the expected
output are given in the files input4_3.txt and output4_3.txt, respectively. Suppose that your program is named
"4", do the followings at the command prompt of the terminal to check if there is any difference between your
output and the expected output.

./4 < input4_3.txt > myoutput.txt
diff myoutput.txt output4_3.txt

Testing against the sample test cases is important to avoid making formatting mistakes. The additional test
cases for grading your work will be of the same formats as the sample test cases.


Coding environment
For Problem 3 and Problem 4, you must make sure that your C++ program can compile, execute and generate
the required outputs on our standard environment, namely, the gcc C++11 environment we have on the CS
Linux servers (academy*). Make sure the following compilation command is used to compile your programs:

g++ -pedantic-errors -std=c++11 [yourprogram].cpp

As a programmer/developer, you should always ensure that your code can work perfectly as expected on a
target (e.g., your client's) environment, not only on yours.

While you may develop your work on your own environment, you should always try your program (compile &
execute & check results) on our standard environment before submission.


Submission
Name your shell script (for Problem 1 and Problem 2) and C++ programs (for Problem 3 and Problem 4) as the
following table shows and put them together into one directory. Make sure that the folder contains only these
source files (*.sh / *.cpp) and no other files. Compress this directory as [uid].zip file where [uid] is your
university number and check carefully that the correct file have been submitted. We suggest you to download
your submitted file from Moodle, extract them, and check for correctness. You will risk receiving 0 marks for
this assignment if you submit incorrect files. Resubmission after the deadline is not allowed.

Filename Description
1.sh Problem 1
2.sh Problem 2
3.cpp Problem 3
4.cpp Problem 4


Late submission
If you submit n days after the deadline, there will be 20n% mark deduction. The 24 hours right after the
deadline is considered as 1 day, and so on so forth. In another word, no mark will be given if you submit after 5
days.


Evaluation
Your code will be auto-graded for technical correctness. In principle, we use test cases to benchmark your
solution, and you may get zero marks for not being able to pass any of the test cases. Normally partial credits
will not be given for incomplete solution, as in many cases the logic of the programs are not complete and an
objective assessment could be difficult. However, your work may still be considered on a case-by-case basis
during the rebuttal stage.

Academic dishonesty
We will be checking your code against other submissions in the class and from the Internet for logical
redundancy. Please be reminded that no matter whether it is providing your work to others, assisting others to
copy, or copying others will all be considered as committing plagiarism and we will follow the departmental
policy to handle such cases. Please refer to the course information notes for details.


Getting help
You are not alone! If you find yourself stuck on something, post your questions to the course forum, send us
emails or come to our support sessions. We want this assignment to be rewarding and instructional, not
frustrating and demoralizing. But we don’t know when or how to help unless you ask.


Discussion forum
Please be careful not to post spoilers. Please don’t post any code that is directly related to the assignments.
However, you are welcome and encouraged to discuss general ideas on the discussion forums. If you have any
questions about this assignment you should post them in the discussion forums.





A. Shell Programming [45%]

A certain railway company in Hong Kong uses a signaling system to keep track of trains in its railway system.
The system generates a log file (.txt) every day. Each line in the log file represents a train calling at a station
and has the following format:

[time_HH:MM:SS], [train_id], [station_id], [paltform_no.]

Each column is separated by a comma “,” in the log file.
The log files have “Trains_” as prefix in their file names, followed by a date in form of YYYY-MM-DD.
The records are sorted by time in ascending order

Field Description
time_HH:MM:SS The time has the format HH:MM:SS
train_id Identify a train
Train ID starting with “E” represents a passenger train. (e.g E201, E217)
Train ID starting with a number represents a maintenance train. (e.g. 8001, 59)
station_id Identify a station
platform_no. The platform number in that particular station

Example:
Consider an example Trains_2022-09-01.txt that stores the records on 2022-09-01.

06:01:10,E201,SHS,1
06:06:28,E209,SHS,1
...
07:10:27,8001,MOK,2
...

From the log file, we know that the E201 passenger train called at SHS station platform No.1 at time 06:01:10.


Problem 1 [20%]:
Create a shell script 1.sh that performs the following:
1. For each “Trains_” log file, find out the three busiest stations that have the most number of passenger
trains calling at. The output should display the count of passenger trains that called at that station and
the station ID.
2. If two or more stations have the same count, we output them in alphabetical order of the station ID.
Therefore “4 FAN” is put ahead of “4 HHK” under “Trains_2022-09-03.txt” in the example below.

If we run 1.sh, the following will output. The sample output can be found in the file output1.txt.
Trains_2022-09-01.txt:
25 LMC
23 TWO
22 FAN
Trains_2022-09-02.txt:
30 SHS
24 LMC
24 SHT
Trains_2022-09-03.txt:
4 FAN
4 HHK
4 KOT
Trains_2022-09-04.txt:
17 SHS
11 MOK
9 FAN



Problem 2 [25%]:
Create a shell script 2.sh that performs the following:
1. The 2.sh takes one command line input argument, which represents the train ID of a train that we would
like to trace.
2. The 2.sh generates a file .txt that contains a list of stations called by the train in all “Trains_”
log files, organized by the filenames and the records in the order of Date and Time.
3. If the number of input arguments is not 1, then the error message “Usage: ./Train_trace.sh ”
should be output in shell prompt.
4. If there is no train record found, then the log file will be deleted (or no need to generate it). The script
should outputs “No records found for train id” in shell prompt. (where id is the train ID inputted by the
user).

For example, If we run:
$ ./2.sh E201

The shell script will generate a file “E201.txt” that contains the following contents:
Trains_2022-09-01.txt
06:01:10,E201,SHS,1
06:19:13,E201,FAN,2
06:48:48,E201,FTR,3
…
Trains_2022-09-02.txt
06:00:50,E201,SHS,1
06:23:40,E201,HHK,3
…
23:15:24,E201,SHS,1
Trains_2022-09-03.txt
Trains_2022-09-04.txt


Sample Test Cases:
2_1
$ ./2.sh E201
E201.txt will be generated. Please refer to the files given.

2_2
$ ./2.sh E209
E209.txt will be generated. Please refer to the files given.

2_3
$ ./2.sh E213
E213.txt will be generated. Please refer to the files given.

2_4
$ ./2.sh E229
E229.txt will be generated. Please refer to the files given.

2_5
$ ./2.sh 8001
8001.txt will be generated. Please refer to the files given.



B. C++ Programming [50%]

Problem 3 [20%]:
Write a program 3.cpp to read an integer N and then print all prime numbers in the range [1, N]. A prime
number is a natural number greater than 1 that has no positive divisors other than 1 and itself.

Hint: For each number M in the range [2, N], you have to check whether it is divisible by any number in the
range [2, M – 1] in order to determine if it is a prime number.

Sample Test Cases:
User inputs are shown in blue.
3_1
10
2
3
5
7

3_2
50
2
3
5
7
11
13
17
19
23
29
31
37
41
43
47

3_3
100
2
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71
73
79
83
89
97



Problem 4 [30%]:
Write a C++ program 4.cpp which encrypts and decrypts some input characters using the Caesar Shifting
algorithm detailed below.
Input:
• A line of input s k c1 c2 c3 …, where
o s is either the character e for encryption, or the character d for decryption
o k is an integer for the number of shifts used in the Caesar shift algorithm (key for encryption or
decryption)
o c1 c2 c3 … is a sequence of space separated characters, ended by !, to be encrypted or
decrypted
Output:
• The encrypted/decrypted message ended by !. No space between two consecutive characters.

Algorithm:
To encrypt (decrypt) a letter c (within the alphabet A-Z or a-z) with a shift of k positions:
1. Let x be c’s position in the alphabet (0 based), e.g., position of B is 1 and position of g is 6.
2. For encryption, calculate y = x + k modulo 26;
For decryption, calculate y = x − k modulo 26.
Here modulo is equivalent to remainder in mathematics.
3. Let w be the letter corresponding to position y in the alphabet. If c is in uppercase, the encrypted
(decrypted) letter is w in lowercase; otherwise, the encrypted (decrypted) letter is w in uppercase.

A character which is not within the alphabet A-Z or a-z will remain unchanged under encryption or
decryption.
Example. Given letter B and k = 3, we have x = 1, y = 1 + 3 mod 26 = 4, and w = E. As B is in uppercase, the
encrypted letter is e.

Requirement:
• Implement a function CaesarShift() which takes in a char c and an int k, where c is the character to
undergo Caesar Shifting and k is the number of positions (can be negative) to shift, and return the
processed char after Caesar Shifting. The returned char is c if c is not within the alphabet range. The
prototype of the function is given by: char CaesarShift(char c, int k).
• You can ONLY use the simple data types char, bool, int, double. In other words, you are not allowed
the use other data types or data structures such as strings, arrays, vectors, etc.

Sample Test Cases:
User inputs are shown in blue.
4_1
e 1 !
!

4_2
e 3 a B c D e !
DeFgH!

4_3
d 3 D e F g H !
aBcDe!

4_4
e -1 H e l l o E N G G 1 3 4 0 / C O M P 2 1 1 3 !
gDKKNdmff1340/bnlo2113!

4_5
d 10 n 3 V 3 D 3 N _ M Y N 3 _ S C _ N 3 L E Q Q 3 N _ M Y N 3 !
D3l3t3d_cod3_is_d3bugg3d_cod3!










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