Stacks and Queues

Question

Hello I have a stack code and a queue code. I am trying to make a very simple doubly linked list but, I am having a very difficult time understanding how to create a doubly linked list using my stack and queues codes:

this is my stack code:

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

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
customer customer1 = new customer()
{
ID = 101,
Name = "Robert",
Gender = "Male"
};
customer customer2 = new customer()
{
ID = 102,
Name = "Paula",
Gender = "Female"
};
customer customer3 = new customer()
{
ID = 103,
Name = "Mike",
Gender = "Male"
};
customer customer4 = new customer()
{
ID = 104,
Name = "Phyllis",
Gender = "Female"
};

Stack<customer> stackCustomers = new Stack<customer>();
stackCustomers.Push(customer1);
stackCustomers.Push(customer2);
stackCustomers.Push(customer3);
stackCustomers.Push(customer4);

foreach (customer c1 in stackCustomers)
{
Console.WriteLine(c1.ID + " - " + c1.Name);
Console.WriteLine("Items left in stack : " + stackCustomers.Count);
}

customer c1 = stackCustomers.Pop();
Console.WriteLine(c1.ID + " - " + c1.Name);
Console.WriteLine("Total items in the queue = " + stackCustomers.Count);

customer c2 = stackCustomers.Pop();
Console.WriteLine(c2.ID + " - " + c2.Name);
Console.WriteLine("Total items in the queue = " + stackCustomers.Count);

customer c3 = stackCustomers.Pop();
Console.WriteLine(c3.ID + " - " + c3.Name);
Console.WriteLine("Total items in the queue = " + stackCustomers.Count);

customer c4 = stackCustomers.Pop();
Console.WriteLine(c4.ID + " - " + c4.Name);
Console.WriteLine("Total items in the queue = " + stackCustomers.Count);
}
}

public class customer
{
public int ID { get; set; }
public string Name { get; set; }
public string Gender { get; set; }
}
}

This is my queue code:

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

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
customer customer1 = new customer()
{
ID = 101,
Name = "Robert",
Gender = "Male"
};
customer customer2 = new customer()
{
ID = 102,
Name = "Paula",
Gender = "Female"
};
customer customer3 = new customer()
{
ID = 103,
Name = "Mike",
Gender = "Male"
};
customer customer4 = new customer()
{
ID = 104,
Name = "Phyllis",
Gender = "Female"
};

Queue<customer> queueCustomers = new Queue<customer>();
queueCustomers.Enqueue(customer1);
queueCustomers.Enqueue(customer2);
queueCustomers.Enqueue(customer3);
queueCustomers.Enqueue(customer4);

customer c1 = queueCustomers.Dequeue();
Console.WriteLine(c1.ID + " - " + c1.Name);
Console.WriteLine("Total items in the queue = " + queueCustomers.Count);

customer c2 = queueCustomers.Dequeue();
Console.WriteLine(c2.ID + " - " + c2.Name);
Console.WriteLine("Total items in the queue = " + queueCustomers.Count);

customer c3 = queueCustomers.Dequeue();
Console.WriteLine(c3.ID + " - " + c3.Name);
Console.WriteLine("Total items in the queue = " + queueCustomers.Count);

customer c4 = queueCustomers.Dequeue();
Console.WriteLine(c4.ID + " - " + c4.Name);
Console.WriteLine("Total items in the queue = " + queueCustomers.Count);
}
}

public class customer
{
public int ID { get; set; }
public string Name { get; set; }
public string Gender { get; set; }
}
}

is it possible to make a doubly linked list using my stack code and my queue code? if so how exactly do I do it? remember i am just trying to make a very simple doubly linked list using stacks and queues. something very simple that an help me understand it easier. please help. thank you in advance even for just taking the time to look at my question.

Vulpes · Answer

That's making a lot more sense now :) The LinkedList class in the .NET Framework is a doubly-linked list and so you could use that to implement your own stack and queue classes. Below I've changed your stack program so that it now uses a custom stack class (MyStack ) implemented using LinkedList  rather than the .NET Framework Stack class: using System; using System.Collections; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { customer customer1 = new customer() { ID = 101 Name = Robert Gender = Male }; customer customer2 = new customer() { ID = 102 Name = Paula Gender = Female }; customer customer3 = new customer() { ID = 103 Name = Mike Gender = Male }; customer customer4 = new customer() { ID = 104 Name = Phyllis Gender = Female }; MyStack stackCustomers = new MyStack (); stackCustomers.Push(customer1); stackCustomers.Push(customer2); stackCustomers.Push(customer3); stackCustomers.Push(customer4); foreach (customer c in stackCustomers) { Console.WriteLine(c.ID +  -  + c.Name); Console.WriteLine(Items left in stack :  + stackCustomers.Count); } customer c1 = stackCustomers.Pop(); Console.WriteLine(c1.ID +  -  + c1.Name); Console.WriteLine(Total items in the stack =  + stackCustomers.Count); customer c2 = stackCustomers.Pop(); Console.WriteLine(c2.ID +  -  + c2.Name); Console.WriteLine(Total items in the stack =  + stackCustomers.Count); customer c3 = stackCustomers.Pop(); Console.WriteLine(c3.ID +  -  + c3.Name); Console.WriteLine(Total items in the stack =  + stackCustomers.Count); customer c4 = stackCustomers.Pop(); Console.WriteLine(c4.ID +  -  + c4.Name); Console.WriteLine(Total items in the stack =  + stackCustomers.Count); } } public class customer { public int ID { get; set; } public string Name { get; set; } public string Gender { get; set; } } public class MyStack : IEnumerable  IEnumerable { LinkedList nodes = new LinkedList (); public int Count { get { return nodes.Count; } } public void Push(T element) { nodes.AddLast(element); } public T Pop() { if (Count == 0) throw new InvalidOperationException(); T value = nodes.Last.Value; nodes.RemoveLast(); return value; } public IEnumerator GetEnumerator() { return nodes.Reverse().GetEnumerator(); // need to iterate from last to first } IEnumerator IEnumerable.GetEnumerator() { return ((IEnumerable)nodes.Reverse()).GetEnumerator(); } } } The output is the same as before namely: 104 - Phyllis Items left in stack : 4 103 - Mike Items left in stack : 4 102 - Paula Items left in stack : 4 101 - Robert Items left in stack : 4 104 - Phyllis Total items in the stack = 3 103 - Mike Total items in the stack = 2 102 - Paula Total items in the stack = 1 101 - Robert Total items in the stack = 0 Perhaps I could leave it now to you to implement your own MyQueue class. Remember that a stack is a LIFO structure whereas a queue is a FIFO structure.

A A · Answer

the problem is that the instructions of this exercise is as follows..... Implement Stack and Queue classes using base class Doubly Linked List . I worded it incorrectly in my first post it seems but I created a simple stack and a simple queue code but I have to implement my stack and queues in a Doubly linked list but im having a problem doing it. I know a doubly linked list has a nodes and the nodes point to the next node and the one before it but im not really sure how to create a doubly linked list implementing my stack and queue.

Vulpes · Answer

Well you can certainly implement a stack or a queue using a linked list but I've never heard of anyone trying to do this the other way around i.e. implement a linked list using a stack and/or queue. In fact on the face of it it can't be done. The essence of a linked list is that you can insert a node anywhere in the chain. With a stack or queue you can only add a node at one end. If this is some sort of exercise are you sure that you've understood it correctly?