STACK

BZHAR OMER BAHRAM MUHAMMED BAZHDAR HAMAD

Erbil Technical Engineering CollegeInformation System Engineering

WHAT IS STACK?

Stack is modifying the array with a special algorithm called LAST IN FIRST OUT (LIFO)

We use this algorithm a lot , for example in the web browser

When you click on new page then pressing back button you return to the last website not the very first page

Stack Default methods

Push() = for adding new element

Pop() = for removing the last element

top() = for retrieving the last element

isEmpty() = condition if the stack is empty or not

Define array

Int array [ ] = new int [10];

Int pointer = -1;

-1

pointer 0 1 2 3 4 5 6 7 8 9

STACK METHODS , (isEmpty)

Boolean isEmpty() {

if (pointer < 0)

return True; //the stack is empty

else

return false;

}

STACK METHODS , (PUSH)

push (int a)

{

pointer++; //increment pointer by 1

array[pointer]=a; //adding value to last index }

a

pointer0 1 2 3 4 5 6 7 8 9

STACK METHODS , (POP)

pop() {

If(isEmpty())

System.out.println(“the stack is empty”);

else

array[pointer]=0;

pointer--; //decrement pointer by 1

}

a=0-1

pointer 0 1 2 3 4 5 6 7 8 9

Full program to implement stack in javapublic class stack {

static int array[]=new int [10];public static int pointer=-1;

public static boolean isEmpty(){

if(pointer<0)return true;

elsereturn false;

}public static void push(int a){

if(pointer==array.length)System.out.println("Stack is

full");else{pointer++;array[pointer]=a;}}

public static int top(){return array[pointer];

} public static void pop(){ if(isEmpty()) System.out.println("the stack is empty"); else{ System.out.println(array[pointer]+" removed"); array[pointer]=0; pointer--; }} static void print(int arr[]){ for (int i = 0; i < arr.length; i++) {

System.out.print(arr[i]+" ");} }public static void main(String[] args)

{//write push and pop the add print with

argument array to see whats going on}}