Solved

Perform EulerTour for a given directory

Posted on 2007-03-26
4
268 Views
Last Modified: 2013-11-23
I need write a class DirectoryTour to persorm an Euler Tour of a given File (i.e. a root of a directory) and i also write a main program to test it, it will call the methods beforeFirst, afterLast and inBetween. the method beforeFirst should be called the first time the node is vistited, the method afterLast should be called the last time the node is vistited, the method inBetween should be called in between each pair of children.  Finally, the default definiation of these methods should be print out the method name,

i do not know how to write a traversal methods, pls give me some tips

the a root of a directory like this:
c:\test0                        ------folder
c:\test0\one                -------folder
c:\test0\one\one-a      -------file
c:\test0\one\one-b      -------file
c:\test0\three               -------folder
c:\test0\two             -------folder
c:\test0\two\two-a      -------file
c:\test0\two\two-b      -------file


for example, out output should be like:
       beforeFirst: test0
       beforefirst: one
       beforefirst: one-a
       afterLast: one-a
       inBetween: one
       beforefirst: one-b
       afterLast: one-b
       afterLast: one
       inBetween: test0
0
Comment
Question by:ericylr
  • 2
  • 2
4 Comments
 

Author Comment

by:ericylr
ID: 18798762
this is a template from website

import jds.util.BinaryNode;

public class EulerTour {
      public final Object traverse (BinaryNode n, Object info) {
            info = beforeLeft(n, info);
            if (n.leftChild != null)
                  info = traverse(n.leftChild, info);
            info = inBetween(n, info);
            if (n.rightChild != null)
                  info = traverse(n.rightChild, info);
            info = afterRight(n, info);
            return info;
      }

      public Object beforeLeft (BinaryNode nd, Object info)
            { return info; }

      public Object inBetween (BinaryNode nd, Object info)
            { return info; }

      public Object afterRight (BinaryNode nd, Object info)
            { return info; }
}
0
 
LVL 20

Expert Comment

by:gatorvip
ID: 18799284
Tree traversal:
http://en.wikipedia.org/wiki/Traversal

Eulerian path
http://en.wikipedia.org/wiki/Euler_tour

You should take the time to read and understand the concepts.

When you have a tree node (root) with several children, what you can do is recursively traverse and "visit"  each child. The simplest example on a "visit" is to print out the node's content.

Look at the traversal link for a clear illustration of a binary tree traversal (traversal methods).
0
 

Author Comment

by:ericylr
ID: 18801345
I write the DirectoryTour class, is it correct?

import java.lang.*;

public class DirectoryTour{

  public static class File{
        File leftChild, rightChild;
  }

  public Object traverse(File f, Object info) {
      info=beforeFirst(f, info);
      if (f.leftChild!=null)
            info=traverse(f.leftChild, info); // recursive traversal      
      info=inBetween(f, info);
      if(f.rightChild!=null)
            info=traverse(f.rightChild, info); // recursive traversal
      info=afterLast(f, info);
        return info;
  }

  // methods that can be redefined by the subclasses

  public Object beforeFirst(File f, Object info) {
        return info;
  }
 
  public Object inBetween(File f, Object info) {
        return info;
  }
 
  public Object afterLast(File f, Object info) {
        return info;
  }
0
 
LVL 20

Accepted Solution

by:
gatorvip earned 500 total points
ID: 18801699
1. Don't use "File" for the node type, you will confuse that with java.io.File which you will most likely need to use at some point in the project.
2. Think conceptually, a directory can have more than just two children (subfolder) so you can't really use a binary node.
0

Featured Post

Netscaler Common Configuration How To guides

If you use NetScaler you will want to see these guides. The NetScaler How To Guides show administrators how to get NetScaler up and configured by providing instructions for common scenarios and some not so common ones.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Java Options in Zimbra Server 2 54
netstat -ano | find "8000" and taskkill /f /pid 2984 3 57
Apps blocked by Java 9 79
eclipse buid path vs tomcat lib path 10 23
For beginner Java programmers or at least those new to the Eclipse IDE, the following tutorial will show some (four) ways in which you can import your Java projects to your Eclipse workbench. Introduction While learning Java can be done with…
Introduction This article is the last of three articles that explain why and how the Experts Exchange QA Team does test automation for our web site. This article covers our test design approach and then goes through a simple test case example, how …
Viewers will learn about arithmetic and Boolean expressions in Java and the logical operators used to create Boolean expressions. We will cover the symbols used for arithmetic expressions and define each logical operator and how to use them in Boole…
This tutorial covers a practical example of lazy loading technique and early loading technique in a Singleton Design Pattern.

778 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question