Homework 5 - Arrays and Masking

Homework 5 - Arrays and Masking
Notice
For this week's homework, some problems can only be tested after "loading" certain
.mat files as instructed in the hw05.m file. You can load these files three ways before running
test cases: right click the .mat file in your directory and select "Load" OR double click on the
.mat file in your directory OR use the built-in load() function (see function documentation:
https://www.mathworks.com/help/matlab/ref/load.html). If you are writing a test script, it would
be wise to use the load() function appropriately. DO NOT use the load() function in your
function code! To test your function(s), load the .mat file first and then run the function with the
specified inputs just as you have been doing up until now. The Autograder will automatically
load the appropriate .mat files for you before grading your homework. If load() is included in
your function, it will error, and you will not receive credit.

Homework 5 - Arrays and Masking
Function Name: castCharm
Inputs:
1. (double) An MxN array
2. (double) Another MxN array
3. (double) The magic number
Outputs:
1. (double) The first MxN array with replacements made
Function Description:
For your Charms class at Hogwarts, Professor Flitwick asks you to replace some
numbers in an array using magic. However, being more comfortable with a computer than with a
wand, you decide to do it with MATLAB instead. Write a function that takes in two arrays and a
magic number; it should replace all instances of the magic number in the first array with the sum
of all the values in the corresponding positions of the second array. If the magic number does
not exist in the first array, it should just return the original array with no changes.
Example:
magicNum = 2
arr1 = arr2 =
[ 1 2 3 4 [ 4 1 3 4
7 5 9 2 1 2 3 4
2 2 3 5 ] 3 5 3 4 ]
arr1Out =
[ 1 13 3 4
7 5 9 13
13 13 3 5 ]
Notes:
● The two input arrays are guaranteed to have the same dimensions.
Homework 5 - Arrays and Masking
Function Name: quibbler
Inputs:
1. (char) The word to search for
2. (char) An NxN array representing the word search
Outputs:
1. (char) The NxN array with the word "crossed out"
Background:
The editors of The Quibbler, the hottest magazine in print in the wizarding world, want to
spice their next issue up for the readers. To make it more interactive, they are going to add a
word search! As a busy student with your OWLs right around the corner, you don’t want to take
the time to solve these puzzles by hand, so you need to come up with a little magic.
Function Description:
Write a function in MATLAB that solves a word search puzzle. The function will take in
two inputs: the word to search for and a character array representing the word search. You will
find the occurrence of the word in the puzzle and ‘cross it out’ by replacing the letters with ‘#’.
You will then return this updated array.
Example:
If the word to search for is 'owl', an example input puzzle and output are below.
input =
abc abc
owl - ###
xyz xyz
Notes:
● You don’t have to consider diagonals, but must consider the word horizontally forwards
and backwards and vertically forward and backwards (the word can read up, down, left,
or right)
● The word may or may not exist in the search; if there is an occurrence there will only be
one
● If your solution recognizes words that spans across several lines, i.e. recognizing
'wizard' in the puzzle below, that is okay. This edge case will not be tested for grading.
abcwiz
arddef
Hints:
● You may find the strfind() and reshape() functions useful.
Homework 5 - Arrays and Masking
Function Name: sortingSquare
Inputs:
1. (double) An NxN array of positive integers (students to be sorted into a house)
2. (double) A double value n, the dimension of the square array of students to be taken out
Outputs:
1. (double) A NxN square array representing the new array of students and ghosts
Background:
The new Hogwarts first years are waiting in an NxN array so that the Sorting Hat can put
them into their corresponding houses! However, the Hat has a very unique way of picking
students out of the array to be sorted.
Function Description:
Given a random double integer, n, the Hat takes out the students in a square array (size
nxn) from the top right corner of the original NxN array.
However, this new array will most likely be jagged. The Hat would like to preserve the
size and shape of the original array, so it asks ghosts to line up at the end of the array to act as
placeholders for students who were just removed. The ghosts should not replace the students'
positions, but be appended after the last position of the array (end). Ghosts will be represented
by negative ones (-1). Output the final array with both students and ghosts
Example:
Notes:
● n can range from 0 to N (nothing deleted, or everything deleted)
● Students will always be represented by positive integers.
● The output array must be square. How do we know how many -1s to add, if any?
Hints:
● You may find the reshape() function useful for this problem.
Homework 5 - Arrays and Masking
Function Name: spellCheck
Inputs:
1. (char) An NxM array of characters
Outputs:
1. (logical) A logical representing whether the array is a magic square
Banned Functions:
diag(), unique(), trace(), eye(), magic()
Background:
It is up to you to help Ron complete his Charms
homework. He needs to identify which spells are real, and which
ones are made up. The trick is, all of the best spells can be
rearranged into an array such that the ascii values will make a
magic square!
As a reminder, a magic square is a matrix of numbers
where the rows, columns, and diagonals all add up to the same
number. Ron is able to rearrange the letters from the spell into
an array, but since he is a wizard and he has no coding
experience, he is counting on you to examine the arrays to figure out if they are magic or not.
Function Description:
Write a function in MATLAB that takes in an array of characters and checks whether the
corresponding ASCII values create a magic square by outputting a logical. Remember the key
aspects to check for a magic square:
1) the array must be square
2) all elements must be unique
3) all columns and rows add to the same number
4) both diagonals add to the same number as the rows and columns.
Notes:
● A 1x1 matrix is a magic square.
Hints:
● Think about how you can use linear indexing to get the diagonal of the matrix without
using any of the banned functions.
Homework 5 - Arrays and Masking
Function Name: hippogriffCase
Inputs:
1. (char) A string of any length
Outputs:
1. (char) The modified input string, now in hippogriff case
Background:
Buckbeak the Hippogriff is on the run with Sirius Black after slashing Draco Malfoy
during Rubeus Hagrid’s Care of Magical Creatures class. Hagrid misses Buckbeak terribly, so
as his friend (and Hogwarts’ resident expert on MATLAB) you decide to help him out by giving
him a way to receive updates on Buckbeak from Sirius!
Function Description:
To prevent the Malfoys from discovering you are talking about hippogriffs, you decide to
create a new typing convention called hippogriffCase. It is similar in idea to camel case,
although a little more complicated. Here are the rules for your new hippogriffCase:
Given a string...
1. Remove all numbers and punctuation (spaces should remain unchanged).
2. Capitalize the first letter of every word and make sure everything else is lowercase.
3. Shift the sentence around so that the LAST instance of 'hippogriff' becomes the
third word in the sentence.
4. Place any leading spaces at the end of the sentence
Example:
The input:
'Hello there, YOU 7 handsome Hippogriffs!!'
Would become:
'You Handsome HippogriffsHello There '
Notes:
● There will always be at least one space before each word, except the first word, which
may have none.
● There can be leading spaces and/or trailing spaces.
● When shifting, spaces should be considered as part of the words they precede.
● The total number of spaces in the input string should equal the total number of spaces in
the output string.
● 'hippogriff' can appear in the input string in any case (upper, lower or both).
Homework 5 - Arrays and Masking
● 'hippogriff' may be a substring of another word. For example, 'hippogriffology',
in which case the output word should be 'Hippogriffology' and should be the 3rd
word in the sentence.
● If 'hippogriff' is present as a substring, then you are NOT guaranteed that it will be at
the beginning of the word. For example, 'anti-Hippogriffs' could appear in the input
string and should be outputted as 'Antihippogriffs'
● You are guaranteed that 'hippogriff' will appear at least once in the input string.
● You are guaranteed that the last instance of 'hippogriff' will be after the second word
in the input string.
Homework 5 - Arrays and Masking
Extra Credit
Function Name: puzzleBox
Inputs:
1. (char) A jumbled character array
2. (double) The row shift vector
3. (double) The column shift vector
Outputs:
1. (char) The solved character array
Banned Functions:
circshift()
Background:
Harry Potter is the "Chosen One", and "The Boy Who Lived", but even he, with all the
power to defeat "You-Know-Who", is struggling to solve a simple Puzzle Box and needs your help
to do it! The Resurrection Stone may be inside, so it is imperative that you help! Should you
chose not to, the world may fall into darkness.
Function Description
Write a function called puzzleBox that will take in a jumbled character array and two
vectors (representing a row shift and a column shift) and produce a satisfying ASCII image. The
last elements in the row and column shift vectors represent the number of shifts to make, while
all other numbers in the vector represent which row/columns to shift.
For example, if the row shift vector was [3, 5, 12, 7], this would indicate that you
should shift every element in row 3, 5 and 12 to the right by 7 columns (shifts should wrap
around to column 1 if they go past the right edge of the array). Positive row shifts move
elements to the right and positive column shifts move elements down. Negative shifts move in
the opposite direction. Your code should be formatted such that the rows slide first, and then the
columns.
Example:
Given the following inputs:
jumbledCharArr = rowShift = [1, 3, 2];
['abc';...
'def';...
'ghi'] colShift = [2, -5];
You should first shift rows 1 and 3 by 2 elements to the right (wrapping elements around
the end of each column). This procedure will produce the array:
Homework 5 - Arrays and Masking
afterRowShift =
['bca';...
'def';...
'Hig']
Then you should shift column 2 by 5 elements up (wrapping elements around the end of
each row). Because the array is a 3x3, shifting by 5 in the upward direction is equivalent to
shifting by 1 in the downward direction (*cough* mod() *cough*). Therefore, the final character
array produced by these inputs is:
finalCharArr =
['bia';...
'dcf';...
'heg']
Notes:
● The shift value can be any integer.
● The index elements will always consist of valid row/column indices
Hints:
● You will find the mod() function very useful.
● Character arrays are just normal arrays in disguise.