diff --git a/DataStructures/Stacks/Stacks.java b/DataStructures/Stacks/Stacks.java deleted file mode 100644 index 2861ef5c..00000000 --- a/DataStructures/Stacks/Stacks.java +++ /dev/null @@ -1,240 +0,0 @@ -import java.util.ArrayList; - -/** - * This class implements a Stack using two different implementations. - * Stack is used with a regular array and Stack2 uses an ArrayList. - * - * A stack is exactly what it sounds like. An element gets added to the top of - * the stack and only the element on the top may be removed. This is an example - * of an array implementation of a Stack. So an element can only be added/removed - * from the end of the array. In theory stack have no fixed size, but with an - * array implementation it does. - * - * @author Unknown - * - */ -class Stack{ - /** The max size of the Stack */ - private int maxSize; - /** The array representation of the Stack */ - private int[] stackArray; - /** The top of the stack */ - private int top; - - /** - * Constructor - * - * @param size Size of the Stack - */ - public Stack(int size){ - maxSize = size; - stackArray = new int[maxSize]; - top = -1; - } - - /** - * Adds an element to the top of the stack - * - * @param value The element added - */ - public void push(int value){ - if(!isFull()){ //Checks for a full stack - top++; - stackArray[top] = value; - }else{ - resize(maxSize*2); - push(value);// don't forget push after resizing - } - } - - /** - * Removes the top element of the stack and returns the value you've removed - * - * @return value popped off the Stack - */ - public int pop(){ - if(!isEmpty()){ //Checks for an empty stack - return stackArray[top--]; - } - - if(top < maxSize/4){ - resize(maxSize/2); - return pop();// don't forget pop after resizing - } - else{ - System.out.println("The stack is already empty"); - return -1; - } - } - - /** - * Returns the element at the top of the stack - * - * @return element at the top of the stack - */ - public int peek(){ - if(!isEmpty()){ //Checks for an empty stack - return stackArray[top]; - }else{ - System.out.println("The stack is empty, cant peek"); - return -1; - } - } - - private void resize(int newSize){ - //private int[] transferArray = new int[newSize]; we can't put modifires here ! - int[] transferArray = new int[newSize]; - - //for(int i = 0; i < stackArray.length(); i++){ the length isn't a method . - for(int i = 0; i < stackArray.length; i++){ - transferArray[i] = stackArray[i]; - stackArray = transferArray; - } - maxSize = newSize; - } - - /** - * Returns true if the stack is empty - * - * @return true if the stack is empty - */ - public boolean isEmpty(){ - return(top == -1); - } - - /** - * Returns true if the stack is full - * - * @return true if the stack is full - */ - public boolean isFull(){ - return(top+1 == maxSize); - } - - /** - * Deletes everything in the Stack - * - * Doesn't delete elements in the array - * but if you call push method after calling - * makeEmpty it will overwrite previous - * values - */ - public void makeEmpty(){ //Doesn't delete elements in the array but if you call - top = -1; //push method after calling makeEmpty it will overwrite previous values - } -} - -/** - * This is an ArrayList Implementation of stack, Where size is not - * a problem we can extend the stack as much as we want. - * - * @author Unknown - * - */ -class Stack2{ - /** ArrayList representation of the stack */ - ArrayList stackList; - - /** - * Constructor - */ - Stack2(){ - stackList=new ArrayList<>(); - } - - /** - * Adds value to the end of list which - * is the top for stack - * - * @param value value to be added - */ - void push(int value){ - stackList.add(value); - } - - /** - * Pops last element of list which is indeed - * the top for Stack - * - * @return Element popped - */ - int pop(){ - - if(!isEmpty()){ // checks for an empty Stack - - int popValue=stackList.get(stackList.size()-1); - stackList.remove(stackList.size()-1); //removes the poped element from the list - return popValue; - } - else{ - System.out.print("The stack is already empty "); - return -1; - } - - } - - /** - * Checks for empty Stack - * - * @return true if stack is empty - */ - boolean isEmpty(){ - if(stackList.isEmpty()) - return true; - - else return false; - - } - - /** - * Top element of stack - * - * @return top element of stack - */ - int peek(){ - return stackList.get(stackList.size()-1); - } - } - -/** - * This class implements the Stack and Stack2 created above - * - * @author Unknown - * - */ -public class Stacks{ - /** - * Main method - * - * @param args Command line arguments - */ - public static void main(String args[]){ - Stack myStack = new Stack(4); //Declare a stack of maximum size 4 - //Populate the stack - myStack.push(5); - myStack.push(8); - myStack.push(2); - myStack.push(9); - - System.out.println("*********************Stack Array Implementation*********************"); - System.out.println(myStack.isEmpty()); //will print false - System.out.println(myStack.isFull()); //will print true - System.out.println(myStack.peek()); //will print 9 - System.out.println(myStack.pop()); //will print 9 - System.out.println(myStack.peek()); // will print 2 - - Stack2 myStack2 = new Stack2(); //Declare a stack of maximum size 4 - //Populate the stack - myStack2.push(5); - myStack2.push(8); - myStack2.push(2); - myStack2.push(9); - - System.out.println("*********************Stack List Implementation*********************"); - System.out.println(myStack2.isEmpty()); //will print false - System.out.println(myStack2.peek()); //will print 9 - System.out.println(myStack2.pop()); //will print 9 - System.out.println(myStack2.peek()); // will print 2 - System.out.println(myStack2.pop()); //will print 2 - } -}