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Assignment 2 – Words

CMPT 225 Assignment 2
Start by downloading the assignment files. This zipfile contains a makefile, a test script and
inputs/ground truths, and stubs for all of the .cpp files you need. Do not create any additional .h
and .cpp files.
The makefile is for use with the linux program ‘make’, which helps compile programs.
The test file is test.py, which is a python file that is executable simply by typing ‘test.py’ at the
linux shell. (or ‘./test.py’ if you don’t have ‘.’ in your PATH)
The testing inputs are the ‘.in’ files, and the expected outputs (called ground truths) are in the
‘.gt’ files.
Stubs are simply placeholders, perhaps with some implementation.
Part 1 – Words
Consider the function shown below. Roughly, the function returns true if the letters in the string s are
in alphabetical order, false otherwise.
Your task
// PRE: s is composed of letters from the English alphabet, with no oth
bool isInAlphabeticalOrder(string s) {
int length = s.size();
for (int i = 0; i < length – 1; ++i) {
if (s[i] s[i+1]) {
return false;
}
}
return true;
}
ASCII
An exact description is that the function isInAlphabeticalOrder returns true if the characters in the string s are in
ASCII order; this differs from alphabetical order in that in ASCII order, all capital letters come before all lowercase ones.
ASCII is the character encoding we most often use for storing and manipulating text on computers. It assigns a
7-bit code to the common characters used in English writing, including numbers, basic math symbols, and
punctuation. Inside memory, we commonly store the 7-bit ASCII code inside the lower bits of an 8-bit byte. Ask
a search engine about “ASCII” to find a chart of which codes (numbers) are assigned to which characters.
8/10/2019 Assignment 2 – Words
www.sfu.ca/~shermer/Teaching/cmpt-225-Summer2019/assignments/assignment2-words.html 2/3
We will be concerned with how many times the character comparison (s[i] s[i+1]) is executed.
First, implement the isInAlphabeticalOrder function in C++ in the file words.cpp. The makefile
contains a definition for words. You can build the executable words for this part of the assignment by
running “make words”. (“make” or “make all” will build both words and the executable for the second
part of the assignment.)
Determine the following for the English words listed in file wordlist (do not convert to lowercase).
1. The average length of a word
2. The average number of character comparisons performed by isInAlphabeticalOrder
3. The average number of character comparisons as a function of the word length.
You will need to add code to isInAlphabeticalOrder (or create a new function) to help you determine
these values.
Note that words.cpp contains code for reading wordlist.
Edit the file word_answers.txt to contain your answers to 1., and 2. above.
The code in words.cpp writes your answer to 3. into a file average_comps.txt. Use the
provided script comps.p to plot this using gnuplot. Running gnuplot comps.p will produce an
image file average_comps.png with a plot in it.
[email protected]: ~$ ls average_comps.txt
average_comps.txt
[email protected]: ~$ gnuplot comps.p
[email protected]: ~$ ls average_comps.png
average_comps.png
Submit word_answers.txt and the gnuplot output average_comps.png with your C++ files from Part
2.
Part 2 – Mode
Write a C++ function that obtains the mode of a set of integers stored in an array. Recall that the
mode of a set is the most frequently occurring element.
Please use the provided file mode.cpp, and fill in the function mode. Note: you must write any
auxialliary functions you use, and may not include any external libraries to help (other than iostream
and fstream). The makefile contains a definition for mode. You can build the executable mode for
this part of the assignment by running “make mode”.
Testing
The zipfile contains a testing script, test.py. You should run this, and other test cases, to verify
correctness of your mode function.
Grading
The assignment is worth 10% and marks are allocated to the assignment as follows:
8/10/2019 Assignment 2 – Words
www.sfu.ca/~shermer/Teaching/cmpt-225-Summer2019/assignments/assignment2-words.html 3/3
Part 1 4%
Part 2 4%
Coding style (memory management, choice of algorithms, use of functions and loops, code
indentation and spacing, comments, and variable naming) 2%
Submission
You should submit your assignment online to the CourSys submission server. You should submit the
following:
Modified words.cpp
Modified word_answers.txt
Plot of number of comparisons as a function of n average_comps.png
Modified mode.cpp

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