/*********************************************************************
**			  CS228 Spring 1997                         **
**		        Solutions For Quiz 2                        **
*********************************************************************/	       

// Problem 1. ( 5 Points )

template <class T>
class Stack {
public:
  Stack();
  void push( T item );
  T pop();
  T top();
  bool isEmpty();
  bool isFull();
private:
  T stackArray[ maxStackSize ];
  int topIndex;
};

// Problem 2. ( 6 Points )

template <class T>
void
Stack<T>::push( T item )
{
  if ( isFull() )
    {
      // Something like this...
      cerr << "Stack Full, item: "
	   << item
	   << " not pushed." << endl;
    }
  else
    {
      stackArray[ ++topIndex ] = item;
    }
  return;
}

// Problem 3. ( 7 Points )

/*********************************************************************

Symbol	|	Postfix Expression		|	Stack
----------------------------------------------------------------------
3	| 3					| 
-	| 3					| -
5	| 3 5					| -
+	| 3 5 -					| +
2	| 3 5 - 2				| +
+	| 3 5 - 2 +				| +
11	| 3 5 - 2 + 11				| +
*	| 3 5 - 2 + 11				| + *
(	| 3 5 - 2 + 11				| + * (
2	| 3 5 - 2 + 11 2			| + * (
-	| 3 5 - 2 + 11 2			| + * ( -
1	| 3 5 - 2 + 11 2 1			| + * ( -
)	| 3 5 - 2 + 11 2 1 -			| + * 
+	| 3 5 - 2 + 11 2 1 - * +		| +
4	| 3 5 - 2 + 11 2 1 - * + 4		| +
*	| 3 5 - 2 + 11 2 1 - * + 4		| + *
6	| 3 5 - 2 + 11 2 1 - * + 4 6		| + *
(end)	| 3 5 - 2 + 11 2 1 - * + 4 6 * +	| 

*********************************************************************/

// Problem 4. ( 7 Points )

// Assume QueueNode defined as follows:
struct QueueNode {
  QueueNode( int I = 0 ) : data( I ) {}
  int data;
  QueueNode * next;
};


void Queue::insert( const int & X )
{
  QueueNode * p, * q;
  
  if ( IsEmpty( ) )
    {
      // Queue is Empty
      front = back = new QueueNode( X );
      back->next = NULL;
    }
  else
    {
      p = q = front;
      // Complete the code for the else part:

      // Check if element should go before the front
      if ( X < frotn->data )
	{
	  front = new QueueNode( X );
	  front->next = p;
	}
      else if ( x >= back->data )   // Inserting after the back
	{
	  back = back->next = new QueueNode( X );
	  back->next = NULL;
	}
      else
	{
	  // X goes somewhere in the middle
	  // first, find where to insert

	  while ( x >= p->data )
	    {
	      q = p;
	      p = p->next;
	    }
	  
	  // Then insert

	  q->next = new QueueNode( X );
	  q->next->next = p;
	}

    } // end else

  return;

}

// There were other ways to do this problem that are equally correct.  
// We used simple input test cases of: 2, 15 and 8 into the diagram
// listed at the bottom of the quiz to determine if a given solution 
// would work.