Category Archives: Computer Science

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, 0, 1}
doubleUp(  { 1, 3 , 1, 5 , 3, 3} ,  3 )    {1 , 3,  , 1, 5 , 3, 3, 3, }

 

 

 

Similar problems on codinbat

Pre4

Mazes 2

Mazes #2

Download Mazes 2 Island Files

 

Shunya Map 1

shunya_1


Shunya 4

shunya_4

 

 

Struhl Map:

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

struhl_map

Ryuki’s Maze

Can be done in about 20 lines

ryuki-maze

 

 

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:

heeyons_maze1

One Solution:heeyeons_maze

 

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
 bretts-maze2

 

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

 Paul’s Diagonal Map
pauls-diagonal

 

 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:
 matts-all-flowers

A Different strategy

matt_water_flower_map


Ryuki’s Red Wind

pick-flowers-red-wind_ryuki

 

Bismark’s Map

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

bismarks-map

 

Sota
sota

EXTRA CREDIT:

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 

islands-3-a-opt


Shunya 3

shunya_3

 


Aliya’s Map

aliya



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

mazes-1-assign-mazes2

 


Shunya 2

shunya_2

 


Yuna’s Original Maze

 

yunas_original_maze


 

 

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

island3-d

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)

diag-inwards-133percent

 

AlanasMessage_MAP.jev

alanasmessage_sped_up


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)

zigazg-opt

5)  Spell Z (Blank Map)

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

spell-z-jeroo-with-loop_assignment-complete


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

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

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

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.

Downloaddownload-bttn the maps

Map #1 : rectangular-lake.jev arrow_right_large
recangular-lake-if2.jev arrow_right_large  
For this one, your Jeroo should travel around the entire outer rim of the island and stop immediately before the flower.
rim-of-lake-1.jev
arrow_right_large  
rectangular-lake-bumps1.jev
arrow_right_large  
Remember Nets kill Jeroosrectangular-lake-bumps2.jev arrow_right_large  
Write a loop that makes the jeroo travel around the lake below. This loop should never end. walk-the-lake-jacks-map.jevs

Printing Digits Of Numbers in Java Assignment

Let’s write the following method

public void printDigits( int n){

}

 

Walk through of how the code should work:

the algorithm inolves

1) extract last digit

2) print last digit

3) remove last digit

keep doing this until there are no more digits

print-numbrs-screen-shot

Example :

Let’s look at printDigits( 345)

Walk through of how the code should work:

the algorithm inolves

1) extract last digit ‘5’

2) print last digit print ‘5’

3) remove last digit now n should be ’34’

do this for ‘4’ and then ‘3’ until there are no more digits

You need a while loop. Think about it. What is the value of n when there are no more digits?