// Originally implemented by Lafore; modifed by Sriram 
// Pemmaraju on Oct 14th, 2007
// Turned into AVLStack on Dec 4th
////////////////////////////////////////////////////////////////
class AVLStack 
   {
   private int maxSize;        // size of stack array
   private AVLNode[] stackArray;
   private int top;            // top of stack
//--------------------------------------------------------------
// This is the constructor that takes as an argument the maximum size
// s that it ever needs to be
   public AVLStack(int s)         // constructor
      {
      maxSize = s;             // set array size
      stackArray = new AVLNode[maxSize];  // create array
      top = -1;                // no items yet
      }
//--------------------------------------------------------------
   public void push(AVLNode j)    // put item on top of stack
      {
      stackArray[++top] = j;     // increment top, insert item
      }
//--------------------------------------------------------------
   public AVLNode pop()           // take item from top of stack
      {
      return stackArray[top--];  // access item, decrement top
      }
//--------------------------------------------------------------
   public AVLNode peek()          // peek at top of stack
      {
      return stackArray[top];
      }
//--------------------------------------------------------------
   public boolean isEmpty()    // true if stack is empty
      {
      return (top == -1);
      }
//--------------------------------------------------------------
   public boolean isFull()     // true if stack is full
      {
      return (top == maxSize-1);
      }
//--------------------------------------------------------------
   }  // end class myStack
////////////////////////////////////////////////////////////////