Hey guys,
i jsut got this assignment and i have 1 week to implement it but i have no idea where to start. The link to the question is http://www.cs.sfu.ca/~mitchell/cmpt-126/a2/a2.pdf
and i have also attached it as a pdf.
the Stack class refered to in the assignment is

class Stack <T> {

  // top of stack
  private Node top ; 

  // Constructor
  public Stack(){ top = null ; }

  // Class for Nodes of Linked List 
  private class Node{
    private T  value ;
    private Node  next ;
    public Node( T value, Node next ){ 
      this.value=value; 
      this.next=next; 
    }
    public T getValue(){ return value; } 
    public Node getNext(){ return next; }
  }

  // returns true iff stack is empty
  public boolean empty(){ 
    return top==null; 
  }

  // pushes <newValue> onto the stack
  public void push( T newValue ){ 
    top = new Node( newValue, top ); 
  }

  // pops top off the stack and returns it
  public T pop(){ 
    T temp = top.getValue();
    top = top.getNext();
    return temp ;
  }

  // returns the top element without popping,
  // returns null if stack is empty
  public T peek(){
    if( !empty() ){
      return top.getValue();
    }else{
      return null ;
    }
  }

  // main method for testing Stack
  public static void main(String [] args){
    System.out.println("Stack Tests");     
    Stack <String> ss = new Stack<String>();
  
    System.out.print( ss.empty() ? "OK" : "not empty!");
    ss.push( "abc" );
    System.out.print( ss.empty() ? "empty!" : "OK" );
    System.out.print( ss.peek().equals("abc") ? "OK" : "top not ``abc''!" ); 
    ss.push( "def" );
    System.out.println( "\n" + ss );
    System.out.print( ss.peek().equals("def") ? "OK" : "top not ``def''!" ); 
    System.out.print( ss.pop().equals("def") ? "OK" : "popped not ``def''!" ); 
    System.out.print( ss.empty() ? "empty!!" : "OK" );
    System.out.print( ss.pop().equals("abc") ? "OK" : "popped not ``abc''!" ); 
    System.out.print( ss.empty() ? "OK" : "not empty!!" );
    System.out.print( ss.peek()==null ? "OK" : "peek not null!" );
    System.out.println( "\n" + ss );

    Stack <Integer> si = new Stack<Integer>();
    si.push(1);
    si.push(2);
    System.out.println( si );
  }

}

if you can gimme anything about how to start this i would be very thnak full.

Thanks in advance.

Attachments

i didnt want anyone to do the hw sorry if it sounded that way. The problem i have is trying to tokenize the entry. i get stuck since the user an type it as 23+5 or 23 + 5. i tried using the hasNext and soo on from the scanner function but it did not seem to work. jsut looking for an idea on how to go about this

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