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Binary Search Tree

1 reply on 1 page. Most recent reply: Nov 18, 2002 10:47 PM by Matt Gerrans

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Monique

Posts: 1
Nickname: loonietune
Registered: Nov, 2002

Binary Search Tree

Posted: Nov 17, 2002 12:01 PM

I need to create an index for text stored in a file(the index gives the line numbers that a word appears on). There are two input files: a text file called "data.txt", for which you build the indiex and a "dismiss" file called "dismiss.txt" which contains a list of words which should not be shown in the index. The output will be placed in a file that your program creates, named "out.txt"

How would you do this using a binary search tree?

I'd appreciate any type of help

Below is what I've come up with so far

import java.awt.*;

import java.awt.event.*;

import java.io.*;

import java.util.*;

public class Program3

{

public static void main(String args[])throws Exception

{

FileReader fr = new FileReader("data.txt");

BufferedReader br = new BufferedReader(fr);

FileReader rf = new FileReader("dismiss.txt");

BufferedReader rb = new BufferedReader (rf);

PrintWriter pw = new PrintWriter(new FileWriter("out.txt"));

String s;

while ((s = br.readLine()) != null)

{

pw.println(s);

}

while ((s = rb.readLine()) != null)

{

pw.println(s);

}

fr.close();

rf.close();

pw.close();

}

public class BST

{

public BST (String val)

{

info = val;

}

String info;

Node left, right;

}

public void insert(String s)

{

}

public void find( String s)

{

}

public class NumList

{

public NumList()

{

}

}

}

Matt Gerrans

Posts: 1153
Nickname: matt
Registered: Feb, 2002

Re: Binary Search Tree

Posted: Nov 18, 2002 10:47 PM

I wouldn't -- I'd use a Map.

What is a Binary Search Tree, anyway? Do you mean binary search, or binary tree? A binary search is a faster way (than linear) of searching a sorted list. A binary tree's keys could be searched this way, of course, but what is really going on in that case is probably a recursive search of the tree, unless all the keys are moved, in order, into a List.

Or are you simply talking about using a TreeMap? In this case, you can just use a Map; it is then quite easy to put any of its implementations behind it (TreeMap, HashMap, Hashtable). If you really need things sorted, then you'd use SortedMap and you'd be pretty much limitted to TreeMap.

I think the more important issue here is how you index words -- for instance, you'll want to make it case-insensitive and be sure to strip out all punctuation and ignore non-words, in addition to those words you are filtering.

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