import java.io.*;

import java.util.*;

import TreePackage.*;

/**

* PreToPost will take an expression in prefix notation and convert it

into postfix using

* a binary tree.

*

* @author Charles Hoot

* @version 4.0

*/

public class PreToPost

{

public static void main(String args[])

{

BinaryTree expression = null;

String toParse = getExpressionString();

//ADD CODE HERE TO GET THE EXPRESSION TREE AND THEN ITERATE OVER

//IT TO PRODUCE THE POST FIX EXPRESSION

}

/**

* Get the tree from the pre order expression tokens recursively

*

* @param expressionParser a Scanner that holds the tokens in pre

order

* @return a Binary tree hold the expression

*/

private static BinaryTree getTree(Scanner expressionScanner)

{

BinaryTree result = null;

// ADD CODE TO RECURSIVELY CONSTRUCT THE BINARY TREE FROM THE

PREFIX

// EXPRESSION HERE

return result;

}

/**

* getExpressionString - Get the string with the expression.

*

* @return A String from the keyboard.

*/

private static String getExpressionString()

{

Scanner input;

String inString = "";

try

{

input = new Scanner(System.in);

System.out.println("Please enter a prefix expression");

inString = input.nextLine().trim();

}

catch(Exception e)

{

System.out.println("There was an error with System.in");

System.out.println(e.getMessage());

System.out.println("Will use the expression + a b / c");

inString = "+ a b / c";

}

return inString;

}

}