using System;

public class Program

{

    public static void Main()

    {

        // create Object of Implementing class  

        StackUsingArray obj = new StackUsingArray(4);  

        // insert Stack value  

        obj.Push(11);  

        obj.Push(22);  

        obj.Push(33);  

        obj.Push(44);  

        // print Stack elements  

        obj.Display();  

        // pritn Top element of Stack  

        Console.Write("\nTop element is {0}\n", obj.Peek());  

        // Delete top element of Stack  

        obj.Pop();  

        obj.Pop();  

        // pritn Stack elements  

        obj.Display();  

        // print Top element of Stack  

        Console.Write("\nTop element is {0}\n", obj.Peek());  

    }

}

​

​

​

public class ListNode

{

    public int val;

    public ListNode next;

    public ListNode(int val)

    {

        this.val = val;

    }

}

​

public class StackUsingArray

{

    int top;

    int[] ele;

    int max;

    public StackUsingArray(int max)

    {

        this.max = max;

        ele = new int[max];

        top = -1;

    }

    public void Push(int val)

    {

        if(top == max-1)

        {

            Console.WriteLine("Stack is full");

            return;

        }

        ele[++top] = val;

        return;

    }

    public int Pop()

    {

        if(top == -1)

        {

            return -1;

        }

        var result = ele[top--];

        return result;

    }

    public int Peek()

    {

        if(top == -1)

        {

            return -1;

        }

        return ele[top];

    }

    public void Display()

    {

        if(top == -1)

        {

            Console.WriteLine("Stack is empty");

        }

        else

        {

            for(var i=0; i<=top; i++)

            {

                Console.Write(ele[i] + "=>");               

            }

        }

    }

}