使用DoubleLinkedList扩展类，允许Add,Remove,Contains-优快云博客

本文详细介绍了双链表的实现方式，并通过实例展示了如何进行添加、删除、查找等基本操作。

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方法与SingleLinkedList(单向链表)类似

创建两个泛型类

DoubleLinkedList<T>

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Diagnostics; namespace DevGuideToCollections { /// <summary> /// Represents a strongly typed double linked list. /// </summary> /// <typeparam name="T">Specifies the type of elements in the list.</typeparam> [DebuggerDisplay("Count={Count}")] [DebuggerTypeProxy(typeof(ArrayDebugView))] public class DoubleLinkedList<T> { int m_count; DoubleLinkedListNode<T> m_head; DoubleLinkedListNode<T> m_tail; int m_updateCode; /// <summary> /// Initializes a new instance of the DoubleLinkedList<T> class that is empty. /// </summary> public DoubleLinkedList() { } /// <summary> /// Initializes a new instance of the DoubleLinkedList<T> class that contains the items in the list. /// </summary> /// <param name="items">Adds the items to the end of the DoubleLinkedList(T).</param> public DoubleLinkedList(IEnumerable<T> items) { foreach (T item in items) { AddToEnd(item); } } /// <summary> /// States if the DoubleLinkedList(T) is empty. /// </summary> public bool IsEmpty { get { return m_count <= 0; } } /// <summary> /// Gets the number of elements actually contained in the DoubleLinkedList(T). /// </summary> public int Count { get { return m_count; } } /// <summary> /// Gets the head node of the DoubleLinkedList(T). /// </summary> public DoubleLinkedListNode<T> Head { get { return m_head; } private set { m_head = value; } } /// <summary> /// Gets the tail node of the DoubleLinkedList(T). /// </summary> public DoubleLinkedListNode<T> Tail { get { return m_tail; } private set { m_tail = value; } } /// <summary> /// Checks if the specified data is present in the DoubleLinkedList(T). /// </summary> /// <param name="data">The data to look for.</param> /// <returns>True if the data is found, false otherwise.</returns> public bool Contains(T data) { return Find(data) != null; } /// <summary> /// Removes all items from the DoubleLinkedList(T). /// </summary> public void Clear() { DoubleLinkedListNode<T> tmp; // Clean up the items in the list for (DoubleLinkedListNode<T> node = m_head; node != null; ) { tmp = node.Next; // Change the count and head pointer in case we throw an exception. // this way the node is removed before we clear the data m_head = tmp; if (tmp != null) { tmp.Previous = null; } --m_count; // Erase the contents of the node node.Next = null; node.Previous = null; node.Owner = null; // Move to the next node node = tmp; } if (m_count <= 0) { m_head = null; m_tail = null; } ++m_updateCode; } /// <summary> /// Adds the specified value to the DoubleLinkedList(T) after the specified node. /// </summary> /// <param name="node">The node to add the value after.</param> /// <param name="value">The value to add.</param> /// <returns>The newly created node that holds the value.</returns> public DoubleLinkedListNode<T> AddAfter(DoubleLinkedListNode<T> node, T value) { DoubleLinkedListNode<T> newNode = new DoubleLinkedListNode<T>(this, value); AddAfter(node, newNode); return newNode; } /// <summary> /// Adds the specified newNode to the DoubleLinkedList(T) after the specified node. /// </summary> /// <param name="node">The node to add the newNode after.</param> /// <param name="newNode">The node to add.</param> public void AddAfter(DoubleLinkedListNode<T> node, DoubleLinkedListNode<T> newNode) { if (node == null) { throw new ArgumentNullException("node"); } if (newNode == null) { throw new ArgumentNullException("newNode"); } if (node.Owner != this) { throw new InvalidOperationException("node is not owned by this list"); } if (newNode.Owner != this) { throw new InvalidOperationException("newNode is not owned by this list"); } if (node == m_tail) { m_tail = newNode; } if (node.Next != null) { node.Next.Previous = newNode; } newNode.Next = node.Next; newNode.Previous = node; node.Next = newNode; ++m_count; ++m_updateCode; } /// <summary> /// Adds the specified value to the DoubleLinkedList(T) before the specified node. /// </summary> /// <param name="node">The node to add the value before.</param> /// <param name="value">The value to add.</param> /// <returns>The newly created node that holds the value.</returns> public DoubleLinkedListNode<T> AddBefore(DoubleLinkedListNode<T> node, T value) { DoubleLinkedListNode<T> newNode = new DoubleLinkedListNode<T>(this, value); AddBefore(node, newNode); return newNode; } /// <summary> /// Adds the specified newNode to the DoubleLinkedList(T) before the specified node. /// </summary> /// <param name="node">The node to add the newNode before.</param> /// <param name="newNode">The node to add.</param> public void AddBefore(DoubleLinkedListNode<T> node, DoubleLinkedListNode<T> newNode) { if (node == null) { throw new ArgumentNullException("node"); } if (newNode == null) { throw new ArgumentNullException("newNode"); } if (node.Owner != this) { throw new InvalidOperationException("node is not owned by this list"); } if (newNode.Owner != this) { throw new InvalidOperationException("newNode is not owned by this list"); } // We have to find the node before this one if (m_head == node) { newNode.Next = m_head; m_head.Previous = newNode; m_head = newNode; } else { // Set the node before the node we are inserting in front of Next to the new node if (node.Previous != null) { node.Previous.Next = newNode; } newNode.Previous = node.Previous; newNode.Next = node; node.Previous = newNode; } ++m_count; ++m_updateCode; } /// <summary> /// Adds the value to the beginning of the DoubleLinkedList(T). /// </summary> /// <param name="value">The value to add to the beginning of the DoubleLinkedList(T).</param> /// <returns>The newly created node that is holding the value.</returns> public DoubleLinkedListNode<T> AddToBeginning(T value) { DoubleLinkedListNode<T> newNode = new DoubleLinkedListNode<T>(this, value); if (IsEmpty) { m_head = newNode; m_tail = newNode; } else { newNode.Next = m_head; m_head.Previous = newNode; m_head = newNode; } ++m_count; ++m_updateCode; return newNode; } /// <summary> /// Adds the value to the end of the DoubleLinkedList(T). /// </summary> /// <param name="value">The value to add to the end of the DoubleLinkedList(T).</param> /// <returns>The newly created node that is holding the value.</returns> public DoubleLinkedListNode<T> AddToEnd(T value) { DoubleLinkedListNode<T> newNode = new DoubleLinkedListNode<T>(this, value); if (IsEmpty) { m_head = newNode; m_tail = newNode; } else { newNode.Previous = m_tail; m_tail.Next = newNode; m_tail = newNode; } ++m_count; ++m_updateCode; return newNode; } /// <summary> /// Locates the first node that contains the specified data. /// </summary> /// <param name="data">The data to find.</param> /// <returns>The node that contains the specified data, null otherwise.</returns> public DoubleLinkedListNode<T> Find(T data) { if (IsEmpty) { return null; } EqualityComparer<T> comparer = EqualityComparer<T>.Default; // Traverse the list from Head to tail for (DoubleLinkedListNode<T> curr = Head; curr != null; curr = curr.Next) { // Return the node we are currently on if it contains the data we are looking for. if (comparer.Equals(curr.Data, data)) { return curr; } } return null; } /// <summary> /// Removes the first occurrence of the specified item from the DoubleLinkedList(T). /// </summary> /// <param name="item">The item to remove from the DoubleLinkedList(T).</param> /// <returns>True if an item was removed, false otherwise.</returns> public bool Remove(T item) { return Remove(item, false); } /// <summary> /// Removes the first or all occurrences of the specified item from the DoubleLinkedList(T). /// </summary> /// <param name="item">The item to remove from the DoubleLinkedList(T).</param> /// <param name="alloccurrences">True if all nodes should be removed that contain the specified item, False otherwise</param> /// <returns>True if an item was removed, false otherwise.</returns> public bool Remove(T item, bool alloccurrences) { if (IsEmpty) { return false; } EqualityComparer<T> comparer = EqualityComparer<T>.Default; bool removed = false; DoubleLinkedListNode<T> curr = Head; while (curr != null) { // Check to see if the current node contains the data we are trying to delete if (!comparer.Equals(curr.Data, item)) { // Assign the current node to the previous node and the previous node to the current node curr = curr.Next; continue; } // Create a pointer to the next node in the previous node if (curr.Previous != null) { curr.Previous.Next = curr.Next; } // Create a pointer to the previous node in the next node if (curr.Next != null) { curr.Next.Previous = curr.Previous; } if (curr == Head) { // If the current node is the head we will have to assign the next node as the head Head = curr.Next; } if (curr == Tail) { // If the current node is the tail we will have to assign the previous node as the tail Tail = curr.Previous; } // Save the pointer for clean up later DoubleLinkedListNode<T> tmp = curr; // Advance the current to the next node curr = curr.Next; // Since the node will no longer be used clean up the pointers in it tmp.Next = null; tmp.Previous = null; tmp.Owner = null; // Decrement the counter since we have removed a node --m_count; removed = true; if (!alloccurrences) { break; } } if (removed) { ++m_updateCode; } return removed; } /// <summary> /// Removes the specified node from the DoubleLinkedList(T). /// </summary> /// <param name="node">The node to remove from the DoubleLinkedList(T).</param> public void Remove(DoubleLinkedListNode<T> node) { if (IsEmpty) { return; } if (node == null) { throw new ArgumentNullException("node"); } if (node.Owner != this) { throw new InvalidOperationException("The node doesn't belong to this list."); } DoubleLinkedListNode<T> prev = node.Previous; DoubleLinkedListNode<T> next = node.Next; // Assign the head to the next node if the specified node is the head if (m_head == node) { m_head = next; } // Assign the tail to the previous node if the specified node is the tail if (m_tail == node) { m_tail = prev; } // Set the previous node next reference to the removed nodes next reference. if (prev != null) { prev.Next = next; } // Set the next node prev reference to the removed nodes prev reference. if (next != null) { next.Previous = prev; } // Null out the removed nodes next and prev pointer to be safe. node.Previous = null; node.Next = null; node.Owner = null; --m_count; ++m_updateCode; } /// <summary> /// Copies the elements of the DoubleLinkedList(T) to a new array. /// </summary> /// <returns>An array containing copies of the elements of the DoubleLinkedList(T).</returns> public T[] ToArray() { T[] retval = new T[m_count]; int index = 0; for (DoubleLinkedListNode<T> i = Head; i != null; i = i.Next) { retval[index] = i.Data; ++index; } return retval; } /// <summary> /// Copies the elements of the DoubleLinkedList(T) from back to front to a new array. /// </summary> /// <returns>An array containing copies of the elements of the DoubleLinkedList<T>.</returns> public T[] ToArrayReversed() { T[] retval = new T[m_count]; int index = 0; for (DoubleLinkedListNode<T> i = Tail; i != null; i = i.Previous) { retval[index] = i.Data; ++index; } return retval; } } }
DoubleLinkedListNode

static void TestDoubleLinkedList() { DoubleLinkedList<int> list = new DoubleLinkedList<int>(); //Testing add list.AddToEnd(6); list.AddToEnd(9); DoubleLinkedListNode<int> nodeAddAfter = list.AddToEnd(5); System.Diagnostics.Debug.Assert(list.Count == 3); DoubleLinkedListNode<int> nodeAddBefore1 = list.AddToBeginning(4); list.AddToBeginning(1); list.AddBefore(nodeAddBefore1, 3); System.Diagnostics.Debug.Assert(list.Count == 6); DoubleLinkedListNode<int> nodeAddBefore2 = list.AddToEnd(7); list.AddAfter(nodeAddAfter, 6); list.AddBefore(nodeAddBefore2, 9); list.AddBefore(nodeAddBefore2, 9); System.Diagnostics.Debug.Assert(list.Count == 10); // Check the next links DoubleLinkedListNode<int> node = list.Head; System.Diagnostics.Debug.Assert(node.Data == 1); node = node.Next; System.Diagnostics.Debug.Assert(node.Data == 3); node = node.Next; System.Diagnostics.Debug.Assert(node.Data == 4); node = node.Next; System.Diagnostics.Debug.Assert(node.Data == 6); node = node.Next; System.Diagnostics.Debug.Assert(node.Data == 9); node = node.Next; System.Diagnostics.Debug.Assert(node.Data == 5); node = node.Next; System.Diagnostics.Debug.Assert(node.Data == 6); node = node.Next; System.Diagnostics.Debug.Assert(node.Data == 9); node = node.Next; System.Diagnostics.Debug.Assert(node.Data == 9); node = node.Next; System.Diagnostics.Debug.Assert(node.Data == 7); // Check the previous links node = list.Tail; System.Diagnostics.Debug.Assert(node.Data == 7); node = node.Previous; System.Diagnostics.Debug.Assert(node.Data == 9); node = node.Previous; System.Diagnostics.Debug.Assert(node.Data == 9); node = node.Previous; System.Diagnostics.Debug.Assert(node.Data == 6); node = node.Previous; System.Diagnostics.Debug.Assert(node.Data == 5); node = node.Previous; System.Diagnostics.Debug.Assert(node.Data == 9); node = node.Previous; System.Diagnostics.Debug.Assert(node.Data == 6); node = node.Previous; System.Diagnostics.Debug.Assert(node.Data == 4); node = node.Previous; System.Diagnostics.Debug.Assert(node.Data == 3); node = node.Previous; System.Diagnostics.Debug.Assert(node.Data == 1); // Deleting the first 6 from the list list.Remove(6, false); System.Diagnostics.Debug.Assert(list.Contains(6)); //System.Diagnostics.Debug.Assert(list[5] == 6); System.Diagnostics.Debug.Assert(list.Count == 9); // Deleting all 9s from the list list.Remove(9, true); System.Diagnostics.Debug.Assert(!list.Contains(9)); System.Diagnostics.Debug.Assert(list.Count == 6); // Check the DebugView method ArrayDebugView view = new ArrayDebugView(list); object[] values = view.Items; System.Diagnostics.Debug.Assert(values.Length == list.Count); int i = 0; for (DoubleLinkedListNode<int> tmpNode = list.Head; tmpNode != null; tmpNode = tmpNode.Next) { System.Diagnostics.Debug.Assert((int)values[i++] == tmpNode.Data); } // Testing clear list.Clear(); System.Diagnostics.Debug.Assert(list.Count == 0); list.AddToEnd(99); list.AddToBeginning(66); list.AddToEnd(199); System.Diagnostics.Debug.Assert(list.Head.Data == 66); System.Diagnostics.Debug.Assert(list.Head.Next.Data == 99); System.Diagnostics.Debug.Assert(list.Tail.Previous.Data == 99); System.Diagnostics.Debug.Assert(list.Tail.Data == 199); // Test removing System.Diagnostics.Debug.Assert(list.Remove(66)); System.Diagnostics.Debug.Assert(!list.Remove(68)); }