using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Queue
{
    class Queue
    {
        Node front = null;
        Node rear = null;

        public void push(int val)
        {
            Node tmp = new Node(val);

            if (front == null)
                front = tmp;
            else
                rear.next = tmp;

            rear = tmp;
        }

        public void pop()
        {
            if(front == null)
            {
                Console.WriteLine("Queue is empty");
            }
            front = front.next;
        }

        public int top()
        {
            if (front == null)
            {
                Console.WriteLine("Queue is empty");
            }
            return front.info;
        }

        public bool empty()
        {
            return (front == null);
        }
    }


}
___________________________________________________
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Stack
{
    class Stack
    {
        Node start = null;

        public void push(int val)
        {
            Node tmp = new Node(val);

            if (start != null)
            {
                tmp.next = start;
            }

            start = tmp;
        }

        public void pop()
        {
            if (start == null)
            {
                return;
            }

            start = start.next;
        }

        public int top()
        {
            if (start == null)
            {
                return 0;
            }

            return start.info;
        }

        public bool empty()
        {
            return (start == null);
        }

    }
}
__________________________
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace QueueArray
{
    class Queue
    {
        int front = -1;
        int rear = -1;
        int[] arr = new int[2000];

        public void push(int val)
        {
            if (rear == arr.Length-1)
            {
                Console.WriteLine("overflow");
                return;
            }

            if (front == -1)
            {
                front++;
            }
            arr[++rear] = val;
        }

        public void pop()
        {
            if (front == -1 || front > rear)
            {
                Console.WriteLine("underflow");
            }

            front++;
        }

        public int top()
        {
            return arr[front];
        }

        public bool empty()
        {
            return (front > rear || (front == -1 && rear == -1));
        }
    }
}
_________________________________________________________
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace StackArray
{
    class Stack
    {
        public int[] arr = new int[5];
        public int top = -1;

        public void push(int val)
        {
            if (top  == arr.Length-1)
            {
                Console.WriteLine("overflow");
                return;
            }

            arr[++top] = val;
        }

        public void pop()
        {
            if (top == -1)
            {
                Console.WriteLine("empty");
                return;
            }

            top--;
        }

        public int Top()
        {
            if (top == -1)
            {
                return 0;
            }

            return arr[top];
        }

        public bool isempty()
        {
            return (top == -1);
        }
    }
}
_________________________________________

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Tree
{
    class Tree
    {
        public Node root = null;

        public void insert(int val)
        {
            if (root == null)
            {
                root = new Node(val);
                return;
            }

            root.insertNode(val);
        }

        public void PreOrder(Node x)
        {
            if (x == null) return;
            PreOrder(x.left);

            PreOrder(x.right);

            Console.WriteLine(x.info);
        }

        public void print()
        {
            PreOrder(root);
        }

        /*public int size = 0;
        public void helper(Node x)
        {
            if (x == null) return;

            size++;
            helper(x.left);
            helper(x.right);
        }

        public int count(Node Root)
        {
            helper(Root);
            return size;
        }*/

    }

    class Node
    {
        public int info;
        public Node left;
        public Node right;

        public Node(int val)
        {
            info = val;
            left = right = null;
        }

        public void insertNode(int val)
        {
            if (val >= info)
            {
                if (right == null)
                {
                    right = new Node(val);
                    return;
                }
                right.insertNode(val);
            }
            else
            {
                if (left == null)
                {
                    left = new Node(val);
                    return;
                }
                left.insertNode(val);
            }
        }
    }
}