Category Archives: Computer Science

Matrix Class

Create a class Matrix

int[][] add (int[][] matr1, int[][] matr2)

Description: This method returns the sum of matr1 and matr2

int[][] multiply(int[][] matr1, int[][] matr2)

Description: This method returns the product of matr1 and matr2

2 D Arrays in Java Assignments

Add the following Methods to a class called ArrayFun2D

public void print(int[][] arr)

Description: This method prints each element in the array. This will be a useful method when you are debugging your code and want to test it out to see if it works.

Method Call	return value
print({{1,2} , {3,4}, { 5, 6 } } )	1 2 3 4 5 6

public int sum(int[][] arr)

Description: This method returns the sum of all elements in the array

Method Call	return value
sum({{1,2} , {3,4}, { 5, 6 } } )	21 ( ie 1+2+3+4+5+6)

public String concat(String[][] strs)

Description: This method returns the concatenation of all the elements in the Array

Method Call	return value
concat({{“a”,”xc” }, {“t”, “zoo”}, { “jjkj” } } )	“axctzzoojjkj”

public double mean( int[][] arr)

Description: This method returns the arithmetic mean of the array. Make sure you double check that you are correctly returning results that include decimal values .

Method Call	return value
mean({{2,8} , {4 , 7} } )	5.25 ie (2+8+4+7)/4

public void printRow(int[][] arr, int row)

Description: This method prints all elements in row. This can be (and should be) done with a single loop.

Method Call	return value
printRow({{1,2} , {3,4}, { 5, 6 } } , 1 )	3, 4
printRow( { 5 , 6} , {7, 12, 13 , 5 }, { 5, 6 ,0} } , 2 )	5 , 6, 0

public void printCol(int[][] arr, int col)

Description: This method prints all elements in col.

Method Call	return value
printCol({{1,2} , {3, 4}, { 5, 6 } } , 1 )	2 4 6
printCol( { 5 , 6} , {7, 12, 13 , 5 }, { 12, 6 ,0} } , 0 )	5 7 12
printCol( {12, 13 , 5 }, { 6, 2, 13 ,11} , {1,2 } } , 2 )	5 13

public int maxVal_inRow(int[][] arr, int row)

Description: This method returns the value of the largest number in the given row

Method Call	return value
maxVal_inRow({{1,2} , {3,4}, { 5, 6 } } , 1 )	4
maxVal_inRow ({ { 5 , 6} , {7, 12, 13 , 5 }, { 5, 6 ,0} } , 2 )	6

public int maxVal_inCol(int[][] arr, int col)

Description: This method returns the value of the largest number in the given col

Method Call	return value
maxVal_inCol({{1,2} , {3,4}, { 5, 6 } } , 0 )	5
maxVal_inCol({{1,-2} , {3,-4}, { 5, -5 } } , 1 )	-2

public int[][] changeValues(int[][] table, int val)

Description:This method returns the array with all elements set toval

changeValues(table, 5)

Original Array

1 2

3 4

5 6

Returned Array

5 5

5 5

5 5

public void print_colMajor(int[][] arr)

Description: This method prints each element in the array – using column major order

Method Call	return value
print({{1,2} , {3,4}, { 5, 6 } } )	1 3 5 2 4 6

public int[][] removeVals(int[][] table, int val)

Description: This method returns a version of the 2-d array where val has been removed from all elements

removeValues(table, 5)

Original Array

{1 , 5}

{3, 4}

{5, 6}

Returned Array

{1}

{3, 4}

{6}

int[] twoD_to1D(int[][] arr)

Description: This method takes an input array that is in 2 dimensions and creates a 1 d array . Assume that the array is rectangular (not jagged).

Method Call	return value
twoD_to1D ( {{1,2} , {3,4}, { 5, 6 } } )	{ 1 , 2 , 3 , 4 , 5 , 6 }

Matrices

int[][] add (int[][] matr1, int[][] matr2)

Description: This method returns the sum of matr1 and matr2

how to add matrices

** int[][] multiply(int[][] matr1, int[][] matr2)

Description: This method returns the product of matr1 and matr2

how to multiply matrices

**public int[][] invertValues(int[][] matr)

Description: This method returns the paramater with its values ‘inverted’

Original Array

1 2

3 4

5 6

Returned Array

6 5

4 3

2 1

Two Dimensinal Arrays in Java

Two Dimensional Arrays in Java

  String[][] table =  {
                        {"a","b","c"},
                        {"d","e","f","g"},                        
                        {"g","h"},
                            };

    int table2[][] = {
                        { 1, 4, 5},
                        {5,11,12},                        
                        {22, 45},
                            };

2-D array Demo Code

2 D Array Assignments

Array 3 [ v1]

Warming up

public void printFactors( int n )

Description: This method prints all factors of n

Method Call	return value/output
printFactors( 5)	1 5
printFactors( 6)	1 2 3 6
printFactors( 9 )	1 3 9
printFactors( 15)	1 3 5 15

public int[] getFactors( int n )

Description: This method returns an array populated with the factors on n

Method Call	return value/output
getFactors( 5)	{1,5}
getFactors( 6)	{1,2,3,6}
getFactors( 9 )	{1,3, 9}
getFactors( 15)	{1,3,5}

public int[] removeZeros(int [] nums)

Description: This method returns a version of the input –with all occurrences of 0 , zero, removed

Method Call	return value/output
noZeros( { 3 , 4, 0, 1} )	{ 3, 4, 1}
noZeros( { 0, 5 , 0, 0, 9, 0, 1 , 11} )	{ 5,9,1,11}

** public int[] doubleUp( int [] nums, int val)

Description: This method retuns a version of the input –with all occurances of val duplicated.

Method Call	return value/output
doubleUp( { 3 , 4, 0, 1} , 4 )	{ 3, 4 , 4, 0, 1}
doubleUp( { 1, 3 , 1, 5 , 3, 3} , 3 )	{1 , 3, 3 , 1, 5 , 3, 3, 3, 3 }

Mazes 2

Mazes #2

Download Mazes 2 Island Files

Shunya Map 1

Shunya 4

Struhl Map:

Start 20, 18
go around the interior, get the flower, pick it up.
1 loop only

Ryuki’s Maze

Can be done in about 20 lines

Heeyeon’s Map:

heeyeons_maze.jev
start Jeroo at (23,1) and pick up the flower at that location
go to (1,23)
you may NOT pick a flower or visit a cell that has a flower (See animation at bottom)

Picture at start:

One Solution:

Brett’s Maze 2

Description: Start at 0,0, pick all the flowers then use them to toss() your way through the nets. bretts-maze2

George’s Map : Start at ( 10,0) , facing SOUTH, Use 1 loop and pick the flower

Paul’s Diagonal Map

Matt’s All Flower Map

Map name : matt_water_flower_map.jev

Directions: pick up all the flowers. Use 1 while loop. You can start and end wherever you want. Just make sure that the loop eventually terminates.

One strategy:

A Different strategy

Ryuki’s Red Wind

Bismark’s Map

Directions: Pick all the flowers. Start anywhere ; end anywhere. Don’t die, Make sure the loop ends.

Sota

EXTRA CREDIT:

JSlider Map

Mazes 1

Objective: To use while loops to get the Jeroo to pass through each maze and get the flower. It is possible to write a solution to both of these mazes using a single while loop–albeit this loop will have several( about 5 or 6) if tests! It is important for this problem that you do NOT simply hand code this. To get an A on both of these assignments you must use 1 single while loop per maze.
Download All Island Files

island3-A

Shunya 3

Aliya’s Map

Mazes 2 (start in top left, 1 loop to pick flower)

Shunya 2

Yuna’s Original Maze

island-3-D (start in the top left, and get to the bottom right)

Diagonal Inwards

Fill up the Map

* Use a blank map and have 2 Jeroos fill up every spot with a flower.
Use a single loop (not an infinite one either)

AlanasMessage_MAP.jev

4) ZigZag : Use 1 while loop (not infinite), follow the flowers, picking them up and use those flowers traverse over the nets. Notice where the Jeroo ends (ie your while loop condition)

5) Spell Z (Blank Map)

start at 0 , 0 with 70 flowers.
Use a single while loop to spell a letter z

Last and most definitely not least:

island3-C

This is the deceptively hard and should be done last and only if you want that A+

Done all of the maps? Start on the next set here

Systematically Visit All Cells [Java]

Description: It’s harvest time and Adam must pick all of the flowers on the island. Unfortunately for Adam, he doesn’t know where the flowers are growing. Flowers could be growing anywhere on the island. In order to keep from being too exhausted, he can only visit each cell once, and he cannot try to pick from an empty cell. There are no nets, water features, or other Jeroos on the island. The purpose of this program is to find a systematic way for Adam to visit every cell exactly once, and pick the flowers from the cells that have flowers.

Download all the island files

The Maps

Note: Do not be fooled by how similar the next map is. You will probably have to rewrite some code to complete the next one.

Two Friends Meet

One Saturday morning, two friends, Bugs and Daffy, decide to meet and plant flowers to beautify Santong island. Daffy starts in the Northwest corner facing East with 90 flowers in his pouch. Bugs starts in the Northeast corner facing West with 90 flowers in his pouch. Bugs and Daffy begin hopping toward one another. As they hop, each plants exactly one flower at every location it enters, including its starting location. They meet, facing each other, roughly in the middle of row 0. After a handshake and a little small talk, Bugs and Daffy both turn toward the south and continue planting flowers all the way to the southern edge of the island. When both reach the South Sea, the say goodbye and part. Daffy turns west and plants flowers all the way to the Western Ocean. Bugs turns east and plants flowers all the way to the Eastern Ocean. This is where our story ends. Your task is to write a Jeroo program that will illustrate this story.

One possible solution to this project is represented in the picture below

Luhn Check Assignment

Luhn Check

It is possible to tell if a number could be a valid credit card. Credit cards numbers can be validated against an algorithm known as a Luhn. Read this first.

Luhn Number Generator

http://www.datagenetics.com/blog/july42013/index.html

Counting from the check digit, which is the rightmost, and moving left, double the value of every second digit.

Sum the digits of the products together with the undoubled digits from the original number.

If the total ends in 0 (put another way, if the total modulo 10 is congruent to 0), then the number is valid according to the Luhn formula; else it is not valid.

from : http://www.impuls-imaging.com/wp-content/uploads/2013/07/luhn_algorithm.png

Image from http://www.impuls-imaging.com/wp-content/uploads/2013/07/luhn_algorithm.png

Mod 10+5 Variant Some credit cards use the “Mod 10 plus 5” variant to extend the space of valid card numbers.[citation needed] In this variant, if the sum ends in 0 or 5, the number is considered valid.

from http://www.moneybluebook.com/imagesvr_ce/mbb/luhn-amex-calculation.jpg

A more extensive analysis with good images and an online Luhn Checker (currently blocked by Harrison network filter)

Jeroo Walk The Lake with Loops

Original Project Descriptions is here

Acknowledgement This problem is adapted from one that was created originally by Erica Eddy of The University of Wisconsin – Parkside.

Your jeroo is exploring the outer perimeter of the lake. It starts next to a flower and travels the entire way around the lake. Have your jeroo stop immediately before the flower (using a loop) and then, after the loop is over, your jeroo should pick the flower.

Download download-bttn the maps