Updates

Updates

Author: careermonk

bin/chapter4stacks/DynamicArrayStack.class

@@ -0,0 +1,112 @@
+/*Copyright (c) Dec 21, 2014 CareerMonk Publications and others.
+ * E-Mail           	: [email protected] 
+ * Creation Date    	: 2015-01-10 06:15:46 
+ * Last modification	: 2006-05-31 
+               by		: Narasimha Karumanchi 
+ * File Name			: DynamicArrayStack.java
+ * Book Title			: Data Structures And Algorithms Made In Java
+ * Warranty         	: This software is provided "as is" without any 
+ * 							warranty; without even the implied warranty of 
+ * 							merchantability or fitness for a particular purpose. 
+ * 
+ */
+
+
+package chapter4stacks;
+
+public class DynamicArrayStack{
+	// Length of the array used to implement the stack.
+	protected int capacity;
+
+	// Default array capacity.
+	public static final int CAPACITY = 16;	// power of 2
+	
+	public static int MINCAPACITY=1<<15; // power of 2
+
+	// Array used to implement the stack.
+	protected int[] stackRep;
+
+	// Index of the top element of the stack in the array.
+	protected int top = -1;
+
+	// Initializes the stack to use an array of default length.
+	public DynamicArrayStack() {
+		this(CAPACITY); // default capacity
+	}
+
+	// Initializes the stack to use an array of given length.
+	public DynamicArrayStack(int cap) {
+		capacity = cap;
+		stackRep = new int[capacity]; // compiler may give warning, but this
+									  // is ok
+	}
+
+	// Returns the number of elements in the stack. This method runs in O(1) time.
+	public int size() {
+		return (top + 1);
+	}
+
+	// Testes whether the stack is empty. This method runs in O(1) time.
+	public boolean isEmpty() {
+		return (top < 0);
+	}
+
+	// Inserts an element at the top of the stack. This method runs in O(1) time.
+	public void push(int data) throws Exception {
+		if (size() == capacity)
+			expand();
+		stackRep[++top] = data;
+	}
+
+	private void expand() {
+		int length = size();
+		int[] newstack=new int[length<<1];
+		System.arraycopy(stackRep,0,newstack,0,length);
+		stackRep=newstack;
+	}
+	
+	// dynamic array operation: shrinks to 1/2 if more than than 3/4 empty
+	@SuppressWarnings("unused")
+	private void shrink() {
+		int length = top + 1;
+		if(length<=MINCAPACITY || top<<2 >= length) 
+			return;
+		length=length + (top<<1); // still means shrink to at 1/2 or less of the heap
+		if(top<MINCAPACITY) length = MINCAPACITY;
+		int[] newstack=new int[length];
+		System.arraycopy(stackRep,0,newstack,0,top+1);
+		stackRep=newstack;
+	}
+	
+	// Inspects the element at the top of the stack. This method runs in O(1) time.
+	public int top() throws Exception {
+		if (isEmpty())
+			throw new Exception("Stack is empty.");
+		return stackRep[top];
+	}
+
+	// Removes the top element from the stack. This method runs in O(1) time.
+	public int pop() throws Exception {
+		int data;
+		if (isEmpty())
+			throw new Exception("Stack is empty.");
+		data = stackRep[top];
+		stackRep[top--] = Integer.MIN_VALUE; // dereference S[top] for garbage collection.
+		return data;
+	}
+
+	// Returns a string representation of the stack as a list of elements, with
+	// the top element at the end: [ ... , prev, top ]. This method runs in O(n)
+	// time, where n is the size of the stack.
+	public String toString() {
+		String s;
+		s = "[";
+		if (size() > 0)
+			s += stackRep[0];
+		if (size() > 1)
+			for (int i = 1; i <= size() - 1; i++) {
+				s += ", " + stackRep[i];
+			}
+		return s + "]";
+	}
+}

bin/chapter4stacks/FixedSizeArrayStack.class

@@ -18,7 +18,7 @@ public class FixedSizeArrayStack{
 	protected int capacity;
 
 	// Default array capacity.
-	public static final int CAPACITY = 10;
+	public static final int CAPACITY = 16;	// power of 2
 
 	// Array used to implement the stack.
 	protected int[] stackRep;