Udemy: Master Coding Interview - Linked Lists - #100

using System;

class DoublyLinkedList {
    public class Node {
        public Node next;
        public Node prev;
        public int value;
        
        public Node(int value) {
            this.value = value;
        }
    }
    
    public Node head;
    public Node tail;
    int size = 0;
    
    static void Main() {
        Console.WriteLine("Hello World!");
        
        DoublyLinkedList list = new DoublyLinkedList(10);
        Console.WriteLine("New list:     List = " + list.ToString());
        list.Append(5);
        Console.WriteLine("Append(5):    List = " + list.ToString());
        list.Append(16);
        Console.WriteLine("Append(16):   List = " + list.ToString());
        list.Prepend(8);
        Console.WriteLine("Prepend(8):   List = " + list.ToString());
        list.Insert(6, 1);
        Console.WriteLine("Insert(6, 1): List = " + list.ToString());
        list.Insert(7, 3);
        Console.WriteLine("Insert(7, 3): List = " + list.ToString());
        list.Remove(0);
        Console.WriteLine("Remove(0):    List = " + list.ToString());
        list.Remove(1);
        Console.WriteLine("Remove(1):    List = " + list.ToString());
        list.Remove(3);
        Console.WriteLine("Remove(3):    List = " + list.ToString());
        list.Prepend(11);
        Console.WriteLine("Prepend(11):  List = " + list.ToString());
        list.Append(12);
        Console.WriteLine("Append(12):   List = " + list.ToString());
    }
    
    public DoublyLinkedList(int value) {
        this.head = new Node(value);
        this.tail = this.head;
        this.size = 1;
    }
    
    public void Append(int value) {
        Node item = new Node(value);
        this.tail.next = item;
        item.prev = this.tail;
        this.tail = item;
        this.size++;
    }
    
    public void Prepend(int value) {
        Node item = new Node(value);
        item.next = this.head;
        this.head.prev = item;
        this.head = item;
        this.size++;
    }
    
    public void Insert(int value, int index) {
        Node current = this.head;
        if (index == 0) {
            Prepend(value);
        } else if (index == this.size) {
            Append(value);
        } else {
            int count = 0;
            while (current != null) {
                if (count == index) {
                    Node item = new Node(value);
                    item.next = current;
                    item.prev = current.prev;
                    current.prev.next = item;
                    current.prev = item;
                    break;
                }
                current = current.next;
                count++;
            }
        }
        this.size++;
    }
    
    public void Remove(int index) {
        if (index == 0) {
            this.head = this.head.next;
        } else {
            Node current = this.head;
            int count = 0;
            while (current != null) {
                if (count == index) {
                    if (index == this.size - 1) {
                        this.tail = current.prev;
                        this.tail.next = null;
                    } else {
                        current.next.prev = current.prev;
                        current.prev.next = current.next;
                    }
                    break;
                }
                current = current.next;
                count++;
            }
        }
        this.size--;
    }
    
    public string ToString() {
        string s = "{";
        Node current = this.head;
        int count = 0;
        while (current != null) {
            if (count > 0) {
                s += ", ";
            }
            s += "" + current.value;
            current = current.next;
            count++;
        }
        s += "}";
        return s;
    }
}