Updated Repo Layout

2022-04-01 22:02:39 +01:00
parent 88d84ab448
commit e5fa390608
9 changed files with 17 additions and 17 deletions
--- a/C#/Datastructures/DoublyLinkedList/DoublyLinkedList.cs
+++ b/C#/Datastructures/DoublyLinkedList/DoublyLinkedList.cs
@ -0,0 +1,211 @@
+namespace C_.Datastructures.DoublyLinkedList
+{
+    public class DoublyLinkedList<T>
+    {
+        internal DoublyLinkedListNode<T>? Head { get; set; } = default;
+        internal DoublyLinkedListNode<T>? Tail { get; set; } = default;
+        private int Count { get; set; } = 0;
+
+        public static DoublyLinkedList<T> Create()
+        {
+            //Create a new empty list
+            return new DoublyLinkedList<T>();
+        }
+
+        public static DoublyLinkedList<T> Create(T value)
+        {
+            //Create a new Class with a single item
+            return new DoublyLinkedList<T>()
+            {
+                Head = DoublyLinkedListNode<T>.Create(value, default, default),
+                Count = 1
+            };
+        }
+
+
+        public static DoublyLinkedList<T> Create(DoublyLinkedList<T> list1, DoublyLinkedList<T> list2)
+        {
+            //Create a new list from 2 separate lists
+
+            DoublyLinkedList<T> list;
+
+            list = list1;
+            if (list == default || list.Count == 0) return list2;
+
+            //Find end of list and append fist item of next list
+            if (list2 == default || list.Count == 0) return list;
+
+            DoublyLinkedListNode<T>? end = list.Traverse();
+
+            //Connect up pointers at ajoining section
+            end!.Next = list2!.Head;
+            end!.Next!.Prev = end;
+            end = list2.Tail;
+            list.Count += list2!.Count;
+
+            return list;
+        }
+
+        public T? this[int i]
+        {
+            get
+            {
+                //Check Range
+                if (i >= Count || i < 0) throw new System.Exception("Error! Index out of Bounds");
+
+                //Return Value
+                DoublyLinkedListNode<T>? node = Traverse(i);
+                if (node != default) return node.Value;
+                return default;
+            }
+            set
+            {
+                //Check Range
+                if (i >= Count || i < 0) throw new System.Exception("Error! Index out of Bounds");
+
+                //Change Value
+                DoublyLinkedListNode<T>? node = Traverse(i);
+                node!.Value = value;
+            }
+        }
+        public void Append(T value)
+        {
+            Count++;
+
+            //Set head to new item if list is empty
+            if (Head == null)
+            {//Append item to front of list (End as well)
+                Head = DoublyLinkedListNode<T>.Create(value, default, default);
+                Tail = Head;
+                return;
+            }
+
+            //Append item to the end of the list
+            Tail!.Next = DoublyLinkedListNode<T>.Create(value, default, Tail);
+            Tail = Tail.Next;
+        }
+
+        public void Insert(int index, T value)
+        {
+            Count++;
+            if (index > Count || index < 0) throw new System.Exception("Error! Index outside of Bounds");
+
+            //Set head to new item if list is empty
+            if (index == 0 || Head == null)
+            {
+                Head = DoublyLinkedListNode<T>.Create(value, Head, default);
+                Tail = Head;
+                return;
+            }
+
+            //Set tail to new item if index is the end
+            if (index == Count - 1)
+            {
+                //Decrement count as it will be be re-incremented once appended
+                Count--;
+                Append(value);
+                return;
+            }
+
+            //Fetch point in list and add new item
+            DoublyLinkedListNode<T>? node = Traverse(index - 1);
+            node!.Next = DoublyLinkedListNode<T>.Create(value, node.Next, node);
+
+            //Create backlink in the list
+            if (node.Next.Next != default)
+                node.Next.Next.Prev = node.Next;
+        }
+
+        public void Delete(int index)
+        {
+            Count--;
+            if (index > Count || index < 0) throw new System.Exception("Error! Index outside of Bounds");
+
+            //Check if we are trying to reference the first item
+            if (index == 0 && Head != default)
+            {
+                Head = Head!.Next;
+                if (Head != default)
+                    Head.Prev = default;
+                return;
+            }
+
+            //Set tail to new item if index is the end
+            if (index == Count && Tail != default)
+            {
+                Tail = Tail!.Prev;
+
+                if (Tail != default)
+                    Tail.Next = default;
+                return;
+            }
+
+            DoublyLinkedListNode<T>? node = Traverse(index - 1);
+
+            node!.Next = node.Next!.Next;
+
+            //Connect item after to the the item before the node we are deleting
+            if (node.Next != default)
+            {
+                node.Next.Prev = node;
+            }
+        }
+
+
+        private DoublyLinkedListNode<T>? Traverse()
+        {
+            //Return the final item in the list
+            return Tail;
+        }
+
+        private DoublyLinkedListNode<T>? Traverse(int i)
+        {
+            //Determine whether to start at the start or end of the list
+            int direction = 1;
+            DoublyLinkedListNode<T>? node = Head;
+
+            if (i > (Count / 2))
+            {
+                //reverse direction of search
+                direction = -1;
+                node = Tail;
+                //i becomes the amount of hops left to reach the item
+                i = Count - i - 1;
+            }
+
+            if (node != null)
+            {
+
+                //continue to given point in the list ('i' hops)
+                for (int x = 0; x < i; x++)
+                {
+                    if (direction == 1)
+                    {//Going forwards
+                        node = node!.Next;
+                    }
+                    else
+                    {
+                        node = node!.Prev;
+                    }
+
+                }
+            }
+            return node;
+        }
+        private DoublyLinkedListNode<T>? Next(DoublyLinkedListNode<T> current)
+        {
+            if (current != default)
+                return current.Next;
+
+            return null;
+        }
+
+        private DoublyLinkedListNode<T>? Prev(DoublyLinkedListNode<T> current)
+        {
+            if (current != default)
+                return current.Prev;
+
+            return null;
+        }
+    }
+}
--- a/C#/Datastructures/DoublyLinkedList/DoublyLinkedListNode.cs
+++ b/C#/Datastructures/DoublyLinkedList/DoublyLinkedListNode.cs
@ -0,0 +1,19 @@
+using C_.Datastructures.Generic;
+
+namespace C_.Datastructures.DoublyLinkedList
+{
+    internal class DoublyLinkedListNode<T> : Node<T, DoublyLinkedListNode<T>>
+    {//Inherits from Node
+        public DoublyLinkedListNode<T>? Prev { get; set; } = default;
+
+        public static DoublyLinkedListNode<T> Create(T? value, DoublyLinkedListNode<T>? next, DoublyLinkedListNode<T>? prev)
+        {
+            return new DoublyLinkedListNode<T>
+            {
+                Value = value,
+                Next = next,
+                Prev = prev
+            };
+        }
+    }
+}