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//week 3 1
public class IntegerStack {
    private int maxSize;
    private int[] stackArray;
    private int top;

    // Constructor to initialize the stack with a given maximum size
    public IntegerStack(int size) {
        maxSize = size;
        stackArray = new int[maxSize];
        top = -1; // Initialize top as -1 when stack is empty
    }

    // Method to push an integer onto the stack
    public void push(int value) {
        if (!isFull()) {
            stackArray[++top] = value;
        } else {
            System.out.println("Stack is full. Cannot push element.");
        }
    }

    // Method to pop an integer from the stack
    public int pop() {
        if (!isEmpty()) {
            return stackArray[top--];
        } else {
            System.out.println("Stack is empty. Cannot pop element.");
            return -1; // Return a default value indicating stack underflow
        }
    }

    // Method to display stack contents from top to bottom
    public void displayFromTop() {
        if (!isEmpty()) {
            System.out.println("Stack from top to bottom:");
            for (int i = top; i >= 0; i--) {
                System.out.println(stackArray[i]);
            }
        } else {
            System.out.println("Stack is empty.");
        }
    }

    // Method to display stack contents from bottom to top
    public void displayFromBot() {
        if (!isEmpty()) {
            System.out.println("Stack from bottom to top:");
            for (int i = 0; i <= top; i++) {
                System.out.println(stackArray[i]);
            }
        } else {
            System.out.println("Stack is empty.");
        }
    }

    // Method to display the top element of the stack
    public int stackTop() {
        if (!isEmpty()) {
            return stackArray[top];
        } else {
            System.out.println("Stack is empty.");
            return -1; // Return a default value indicating stack underflow
        }
    }

    // Method to check if the stack is empty
    public boolean isEmpty() {
        return (top == -1);
    }

    // Method to check if the stack is full
    public boolean isFull() {
        return (top == maxSize - 1);
    }

    public static void main(String[] args) {
        IntegerStack stack = new IntegerStack(5);

        stack.push(10);
        stack.push(20);
        stack.push(30);

        stack.displayFromTop();

        System.out.println("Top element: " + stack.stackTop());

        System.out.println("Popped element: " + stack.pop());

        stack.displayFromBot();
    }
}


//week 3 2
class Node {
    int data;
    Node next;

    public Node(int data) {
        this.data = data;
        this.next = null;
    }
}

public class IntegerLinkedList {
    private Node head;

    // Default constructor
    public IntegerLinkedList() {
        head = null;
    }

    // Method to check if the linked list is empty
    public boolean isEmpty() {
        return head == null;
    }

    // Method to display the linked list
    public void display() {
        Node current = head;
        if (isEmpty()) {
            System.out.println("List is empty");
            return;
        }
        System.out.println("Linked list:");
        while (current != null) {
            System.out.print(current.data + " ");
            current = current.next;
        }
        System.out.println();
    }

    // Method to add a node at the end of the linked list
    public void addAtLast(int data) {
        Node newNode = new Node(data);
        if (isEmpty()) {
            head = newNode;
            return;
        }
        Node current = head;
        while (current.next != null) {
            current = current.next;
        }
        current.next = newNode;
    }

    // Method to delete the node at the head of the linked list
    public void deleteAtHead() {
        if (isEmpty()) {
            System.out.println("List is empty. Nothing to delete.");
            return;
        }
        head = head.next;
    }

    public static void main(String[] args) {
        IntegerLinkedList linkedList = new IntegerLinkedList();

        System.out.println("Is list empty? " + linkedList.isEmpty());

        linkedList.addAtLast(10);
        linkedList.addAtLast(20);
        linkedList.addAtLast(30);

        System.out.println("Is list empty? " + linkedList.isEmpty());

        linkedList.display();

        linkedList.deleteAtHead();
        System.out.println("After deleting at head:");
        linkedList.display();
    }
}

//vector demo
import java.util.*;
public class vectordemo
{
public static void main(String arg[])
  {
   Vector v=new Vector();
    int x=10;
    Integer y=new Integer(20);
     String str="pk";
     v.add(x);
     v.add(y);
     v.add(str);
     v.add(2,new Integer(30));
     System.out.println("the elements of vector"+v);
     System.out.println("the size of vector are"+v.size());
     System.out.println("the element at position 2 is"+v.elementAt(2));
System.out.println("the first element of the vector is"+v.firstElement());
v.removeElementAt(2);
System.out.println("the elements of vector is "+v);
System.out.println("the size of vector are"+v.size());

    }
}

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