How To List All Possible Paths From Point A To B By Using Recursion

Apr 12, 2014

From a two-dimensional grid 5x5 that looks like this:

(0,0)(0,1)(0,2)(0,3)(0,4)
(1,0)(1,1)(1,2)(1,3)(1,4)
(2,0)(2,1)(2,2)(2,3)(2,4)
(3,0)(3,1)(3,2)(3,3)(3,4)
(4,0)(4,1)(4,2)(4,3)(4,4)

We have Starting point that is (3,0) and an ending point is (1,3). We can only move up and right to get to the ending point by using recursion. We have to list all possible paths from (3,0) to (1,3)

Example: paths:(3,0)(2,0)(1,0)(1,1)(1,2)(1,3)
(3,0)(2,0)(2,1)(1,1)(1,2)(1,3)
etc...

I was able to get from (3,0) to (1,3) but how to list the other paths. This is my code so far

public class Program7 {
public static void main(String[] args){
int size = 5;
int x1 = 3;
int y1 = 0;
int x2 = 1;
int y2 = 3;
System.out.println(x1+" "+y1);
System.out.println(x2+" "+y2);

[Code] ....

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List All Possible Paths From Point A To B Using Recursion?

Apr 12, 2014

From a two-dimensional grid 5x5 that looks like this:

(0,0)(0,1)(0,2)(0,3)(0,4)
(1,0)(1,1)(1,2)(1,3)(1,4)
(2,0)(2,1)(2,2)(2,3)(2,4)
(3,0)(3,1)(3,2)(3,3)(3,4)
(4,0)(4,1)(4,2)(4,3)(4,4)

We have Starting point that is (3,0) and an ending point is (1,3). We can only move up and right to get to the ending point by using recursion. We have to list all possible paths from (3,0) to (1,3)

Example: paths:(3,0)(2,0)(1,0)(1,1)(1,2)(1,3)
(3,0)(2,0)(2,1)(1,1)(1,2)(1,3)
etc...

I was able to get from (3,0) to (1,3) but how to list the other paths. This is my code so far

public class Program7 {
public static void main(String[] args){

int size = 5;

int x1 = 3;
int y1 = 0;
int x2 = 1;
int y2 = 3;

System.out.println(x1+" "+y1);
System.out.println(x2+" "+y2);

int [][] path = new int[size][size];
grid(path,x1,y1,x2,y2);

[code].....

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Creating A Reverse List - Integer - Using Recursion

Jan 2, 2015

I created this code, seems like it should be working properly and the code is right, but the output is not what it should be.The action gets a List<Integer> and should make it reversed.

As example: 1 2 3 4 5 ---> 5 4 3 2 1

The Nodes in the new list (lst2) should be in a reversed position.The code does compile with no errors.I do have Node<T> and List<T> classes

Java Code:

public class NodeReverse
{
public static void reverse (List<Integer> lst, Node<Integer> node, int counter, List<Integer> lst2, Node<Integer> pos) // Should make lst = lst2 while lst2 is the opposite to lst
{
node = node.getNext();
counter++;
if(node.getNext()!=null)
reverse(lst, node, counter, lst2, pos);

[code]....

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Finding And Printing Median Node In Linked List Using Recursion

Nov 3, 2014

The only problem I have now is getting a method to return the median element of a LinkedList without using loops of any kind or by using a global counter anywhere.

I've pretty easily figured out how to get the index value for the median number (there is some lee way allowed. If the list has an even size, any of the middle values are accepted) but I can't figure out how to print it without loops.

I'm sure I need to make a method that finds an element at the given index value, but I don't know how to do it without loops.

Here's all of my code. Inside is my Assignment3 class I use for testing, StudentList which contains the LinkedList head and other List methods, and StudentNode which is obviously, the Node class. Also I've attached the first test1.txt file as well.

import java.io.FileNotFoundException;
import java.util.*;
public class Assignment3 {
public static void main (String []args){
StudentList<StudentNode> myList = new StudentList<StudentNode>();

[Code] .....

I tried making a method that basically counts up the list recursively then a second method that counts down recursively and is supposed to stop once it hits the middle number, then print that node.

Attached File(s) : test1.txt (106bytes)

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Constructs And Initializes A Point With Same Location As Specified Point Object

Jun 5, 2014

I was reading the oracle java tutorial under: URL....Here's the code for the Point class:

public class Point {
public int x = 0;
public int y = 0;
//constructor
public Point(int a, int b) {
x = a;
y = b;
}
}

and in the Rectangle class you have the following constructor:

public Rectangle(Point p, int w, int h) {
origin = p;
width = w;
height = h;

If we create a new Point object like this:

Point originOne = new Point(23, 94);

and then a new Rectangle object like this:

Rectangle rectOne = new Rectangle(originOne, 100, 200);

Will that set originOne to point to the object Point at (23, 94). just want to make that this is the meaning of this statement: Point(Point p)Constructs and initializes a point with the same location as the specified Point object.

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Displaying All Paths In A Tree

Nov 20, 2014

I know what the tree data structure is, how it works, etc., but I need to design a method that will sequentially print out all the paths in the tree (i.e. for each node).

The method as provided is

private static String getAllPaths(final BinaryNodeInterface<Character> root) { }

Now the string that must be returned needs to be of the format:

root.getData() + " " + path + "
"
root.getData()[1] + " " + path[1] + "
"
etc.

The pseudocode I was thinking of doing was something along the lines of:

paths
if(root.getData() = null) return paths;
path = ?; // absolutely no clue what to do here
paths += root.getData() + " " + path + "
";
if(root.hasLeftChild()) {
newPath += "0";
paths += begin recursion;
}
if(root.hasRightChild()) {
newPath += "1";
paths += begin recursion;
}
return paths;

Problems:

(1) I don't know how to determine "path" before the left and right children check (the root node's path is "", the first left node's path is "0", the first right node's path is "1", pattern continues with left being "0" and right being "1").
(2) I don't know where to put newlines precisely.
(3) I'm not sure how to get the print layout precisely as it is supposed to be. At most I've been able to just get the last number in the sequence (i.e. if it was supposed to be "1000", I could get "0".

I am working with the pseudocode formulation, especially in regards to the logic and formatting. I think once I have an understanding of what is going on, I can solve it. And yes, I've gone through a couple pseudocode rewrites (a few hours worth) and haven't gotten anywhere which is slightly unnerving.

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Apr 25, 2014

I can't get Relative paths to work. I have created the class.dat file and I can't get java to recognize it. I am using Eclipse as an IDE. Was wondering if I could get Eclipse to recognize it. I tried with a .txt file as well and couldn't get that to work.

import java.io.*;
public class ReadBytes
{
public static void main(String[] args)
{
try
{
FileInputStream file = new FileInputStream("class.dat");

[Code] .....

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Sep 14, 2014

I print a path like below with iteration. It is redundant as you see. How can I remove the redundant path? im using arrayList .

1. [0, 1]
2. [0, 1, 2]
3. [0, 1, 3]
4. [0, 1, 3, 4]

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File Paths In Eclipse / Jgrasp

May 1, 2014

So I downloaded jgrasp and eclipse on a new computer and am trying to figure out how their filing/path system works.In eclipse I created a new project under which I've imported all my files for my comp sci class, so they're all under this one project which is my only project. I attached a pic of what my eclipse workspace looks like. In this project folder is a file I'm trying to run.

I keep getting an error saying "editor" does not contain a main type.When I change my class name to the project folder I end up getting an option to run the program as an applet or an application, but either one I choose I get the same error message. In the bottom it gives me a warning saying

DescriptionResourcePathLocationType
Build path specifies execution environment CDC-1.1/Foundation-1.1. There are no JREs installed in the workspace that are strictly compatible with this environment. CS1050AssignmentsBuild pathJRE System Library Problem

I tried running the program in jgrasp and got this error

----jGRASP wedge2 error: command "javac" not found.
---- This command must be in the current working directory or
---- on the current system PATH or jGRASP PATH to use this function.
---- System + jGRASP PATH is "C:UsersQudrat.MommandiDocuments;C:Windowssystem32;C:Program Files (x86)InteliCLS Client;C:Progra

[code]...

I have the JDK installed in program files, I have the correct versions of eclipse and Jgrasp, and have uninstalled / reinstalled the JDK/Jgrasp/Eclipse so I don't know what the problem is?

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Aug 6, 2014

I am trying to make a GUI that allows the user to input the NumberLink puzzle (through mouse action events), and then, displays the puzzle in a grid with features to draw a path, and undo it. This is almost exactly the same functionality as in Numberlink on Nikoli

1. In my project, I have a Stage in which a setup scene prompts user for rows and columns (to take size of puzzle),

2. Then, it generates an empty grid (I'm thinking of using a GridPane here), and the user clicks the squares to enter the numbers into the square. this phase isnt a problem if I use text fields and mouse listeners and store info in a grid... the next phase is what I'm stuck at... unless I know exactly how to do that, I cant make progress...

3. In the third stage, I have to display the numbers to the user just like on the Nikoli site (the highlighting number pairs on mouse hover is a necessary feature too, which I think I can handle with CSS).. and the user should draw paths between the numbers, just as on that site ( I thought VLineTo and HLineTo classes would be suitable.. but I'm not sure, and cant find any alternatives) .....

So with this in mind, I made FXML based dummy gui layouts to test if my ideas work... And I cant get the GridPane to have lines drawing atop it (meaning, I cant place Line objects like HLine on top of the grid panes).... is there any other way to do what I need to do ? I also thought of making canvases in a grid (each square is its own canvas)

How I can implement a user inputted path drawing ??

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May 5, 2015

Is it possible to find the number of paths between two nodes in a directed graph using an adjacency matrix? I know how to find all said paths of a given length by using matrix exponentiation, but I don't know how to find all the paths. The professor didn't note it in the assignment but I assume she meant all simple paths because this is a cyclic graph, so there's a potentially infinite number of paths.

I'm thinking I should use matrix exponentiation to find the number of paths of lengths 1 to n-1, where n is the number of nodes in the graph. Then add the number of paths for each length together. Would this work?

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Oct 18, 2014

I've been pondering about this algorithm for about a week but I'm still not able to write a "fast" working method/algorithm to solve the Number-of-paths-exercise we were given in my class />

So here's the task:
Write an efficient java program "Paths" which solves the following task:

- Read input n ∈ N and give output a(n) which is the number of paths from (0,0) to (n,0)
it is not allowed to go over the diagonal (m,m) and also not below the x-axis (m,0)

Here are the allowed steps:
u = (1,1), U = (1,4), d = (1,−1), D = (1,−4) and H = (1,0)
steps are performed in a two-dimensional-coordinate-system!

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Method Get In Type Paths Is Not Applicable For Argument

Jun 4, 2014

I am using Oracle Java 8 in Eclipse working on both Ubuntu and OSX. I have this code:

Java Code:

private static String getConfigDir(){
Path configDir = Paths.get(homeDir(), homeConfig(), appName());
return configDir.toString();

[code]...

But for the method get() of Paths, I get this error in eclipse.The method get(String, String[]) in the type Paths is not applicable for the argument..Yet on the Oracle documentation site, it uses a similar example:

Path p5 = Paths.get(System.getProperty("user.home"),"logs", "foo.log");

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Jun 5, 2014

I use git as my SCM and I use both Ubuntu and Mac OSX. The home directory of the two operating systems are different and there lies the problem. When I commit the .classpath to version control, it looks something like this:

Java Code:

<classpath>
<classpathentry kind="src" path="src"/>
<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
<classpathentry kind="lib" path="/Users/MyUser/Documents/github/Gateway/GDGateway/java-json.jar"/>
<classpathentry kind="lib" path="/Users/MyUser/Documents/github/Gateway/GDGateway/postgresql-9.3-1101.jdbc41.jar"/>
<classpathentry kind="output" path="bin"/>
</classpath> mh_sh_highlight_all('java');

Now when I update my project on Ubuntu. I have to change the build path again because it is referencing paths on OSX. And this goes back and forth. Rather than remove this file from git with .gitignore, I'd prefer to use a global environment variable like as follows:

Java Code:

<classpath>
<classpathentry kind="src" path="src"/>
<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
<classpathentry kind="lib" path="$HOME/Documents/github/Gateway/GDGateway/java-json.jar"/>
<classpathentry kind="lib" path="$HOME/Documents/github/Gateway/GDGateway/postgresql-9.3-1101.jdbc41.jar"/>
<classpathentry kind="output" path="bin"/>
</classpath> mh_sh_highlight_all('java');

Is this possible?

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Create Compound Shapes / Paths In JavaFX?

Apr 28, 2015

Is there some way to create compound shapes/paths in JavaFX?

For the record I'm not implying the use of the methods intersect, subtract, or union. These produce other shapes. A compound shape/path is one that has a knockout of some sort. For instance, a circle within a circle, such as in a 2d donut shape. Alternatives do not include a circle with a thick stroke nor an overlayed circle with the background color. Specifically, JavaFX supports the FillRule, in the case of the Path object. However, there doesn't appear to be an "add" method as there was in the Area shape in Swing.

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I am developing an web application with servlets and jsp. I have an issue to store images. I am storing images in folder and their relative path's in mysql database.

When I retrieve path from database then using <IMG> tag i have displayed image like:

     out.println("<td><img src="+user.getPlaceImage()+" width='70' height='50' /></td>");

It is working fine with internet explorer but not working (that is Not displaying image) in chrome/mozilla.

How to display that image in all browsers....

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Apr 29, 2014

I am trying to make a game, for some reason i have begun to get a java.lang.StackOverflowError.

I am not exactly sure how i can fix it. only removing line 14 from infopannel1 (and everything that used that class.) seems to work. im not sure what else i can do to fix it. or why its resulting in stack overflow for that matter.

I am putting in a link for the files i wrote this using bluej (several classes have no relevance, errorv2, demonstration, folderreadertest, ReadWithScanner, saveloadtest, menutest,rannum, and menutestTester. are all irrelivent to my problem.)

[URL] .....

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How Does Recursion Work

Dec 13, 2014

how does recursion works, I don't understand why it prints al numbers going up again?This is the code

void print2(int n){
if (n<0){
out.printf(" %d",-1);
return;
}
out.printf(" %d", n);
print2(n-1)
out.printf(" %d", n);
}

this should be the output if n is 6: 6 5 4 3 2 1 0 -1 0 1 2 3 4 5 6.

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Sum Of Array By Recursion

Mar 25, 2015

How to add the sum of an array with a recursion, but I don't understand how to use recursion. I just understand that it calls back the method. I am nearly done with the code.

import java.util.Scanner;
class Question1{
public static void main(String[]args){
Scanner s = new Scanner(System.in);
int size, sum;
System.out.println("Please input how many numbers will be used");
size=s.nextInt();

[Code] .....

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Aug 6, 2014

public void myFunc(MyNode n, ArrayList<MyNode> path) {
boolean hasChildren = false;
path.add(n);
int index = path.indexOf(n);
ArrayList<MyNode> statefulPath = new ArrayList<MyNode>();

[Code] ....

I have similar code that I stepped through in a debugger. After running the code I found that it built the desired tree, in this case a root node H with left child L and right child P. I want list of lists to contain all paths from root to leaf. I expected [H, L] and [H, P]. I discovered that statefulPath is not stateful; after a recursive stack frame pops, statefulPath still contains n! But that stack frame just popped! I expected to see statefulPath be [H] in the debugger and it was [H, L]! So I later have a list [H,L,P] which I don't want. How do I make the statefulPath list I want for my algorithm?

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Increment Counter By Recursion

Mar 22, 2015

I have a question related to the code below, that I do not understand. The aim is to count all files and subdirectories in an ArrayList full of files and subdirectories. So I have to count every file and every subdirectory.

The code concerning counting files is clear to me - every time d is of the type file I have to increment n by one. However I thought that I have to do the same thing in case d is a directory, so I would have written the same code for directories.

So what does "n += ((Directory) d).countAllFiles();" mean? In my understanding the method countAllFiles() is applied again on the object Directory ( as Directory is the class that contains this method), but how is n incremented by this? I thought n should be incremented by one as we did with files.

public int countAllFiles() {
int n = 0;
for(SystemFile d : content) {
if(d instanceof File) {
n++;

[Code] ....

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How Recursion Calls Are Made

Jun 5, 2014

How the recursion works. I tried to figure out writing down low, mid, high at each recursive call. But I seem to be making a mistake somehow. I don't understand where the values are returned to in

if(leftmax>rightmax){
return leftmax;}
else
return rightmax;

Here's the code:

public class Maximum{
public static int max(int[] a,int low,int high){
int mid,leftmax,rightmax;
if(low==high)
return a[low];

[Code] ....

firstly leftmax=max(a,0,4)

Then what is the next line executed?Is it rightmax=max(a,5,8).

After this is it leftmax=max(a,5,6)

rightmax=max(a,7,8)

I tried to understand what these recursion calls by writing them down.But I somehow make a mistake.

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Oct 20, 2014

I just started studying recursion and I wanted to know how to create a palindrome number going up from 1 to n then back to 1 like this: "12345...n...54321".

I've done one going downwards and then upwards like this: "n...4321234...n".

Here's my code:

Java Code: import java.util.*;
public class PalindromeTest
{
public static void downPalindrome(int n)

[Code].....

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Printing Pattern Using Recursion

Jul 16, 2014

The program I'm working on is supposed to read input from a file and using recursion, print the pattern of asterisks for each value until the value is either < 0 or > 25.For example, if the value was 4, the pattern would look like this

*
* *
* * *
* * * *
* * *
* *
*

The values are stored in a file entitled prog3.dat which looks like this

4
3
15
26
0

I've never used recursion before and haven't been able to find anything showing how it would work with this particular type of problem.Here is what I've been able to come up with so far, but I'm having problems still which I will show following the code.

import java.util.Scanner;
import java.io.*;
public class Program3 {
public static void main(String[] args) throws Exception {
int num = 0;
java.io.File file = new java.io.File("../instr/prog3.dat");
Scanner fin = new Scanner(file);

[code]...

It appears to be reading the file correctly, but is only printing the top half of the pattern. Also, like I said, I'm not very familiar with recursion, so am not sure if this is actually recursion?

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Jul 16, 2014

The program I'm working on is supposed to read input from a file and using recursion, print the pattern of asterisks for each value until the value is either < 0 or > 25. For example, if the value was 4, the pattern would look like this
 
*
* *
* * *
* * * *
* * *
* *
*
 
The values are stored in a file entitled prog3.dat which looks like this
 
4
3
15
26
0
 
I've never used recursion before and haven't been able to find anything showing how it would work with this particular type of problem. Here is what I've been able to come up with so far, but I'm having problems still which I will show following the code.
 
import java.util.Scanner; 
import java.io.*;
public class Program3 {
public static void main(String[] args) throws Exception {
int num = 0;
java.io.File file = new java.io.File("../instr/prog3.dat");
Scanner fin = new Scanner(file);

[Code] ....
 
Output:
 
Please enter an integer
*
* *
* * *
* * * *
Please enter an integer
*
* *
* * *
Please enter an integer
 
*
* *
* * *
* * * *
* * * * *
* * * * * *
* * * * * * *
* * * * * * * *
* * * * * * * * *
* * * * * * * * * *
* * * * * * * * * * *
* * * * * * * * * * * *
* * * * * * * * * * * * *
* * * * * * * * * * * * * *
* * * * * * * * * * * * * * *
Please enter an integer
Please enter an integer
 
As you can see, I don't know how to make it print the pattern like in the example and am honestly not even sure if this is recursion since I've never actually worked with recursion before.

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Apr 26, 2015

I was asked to create a word pyramid program using recursion. I understand the concept of recursion (i.e. a method calling itself with the problem it is solving getting simpler and simpler each time) but I am having issues writing the program. Here is my code:

public static void main(String[] args) {
//This program will create a word pyramid by using a recursive algorithm.
//For example, the output of "DOGGY" should be:
//DOGGY
//OGG
//G
//This program will also use a recursive algorithm to accomplish this.
String userWord = JOptionPane.showInputDialog(null, "Hello and welcome to the Word Pyramid program."

[Code] .....

So, if I input HORSE the output should be:

HORSE
ORS
R

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