C#數據構造之雙向鏈表(DbLinkList)實例詳解。本站提示廣大學習愛好者：（C#數據構造之雙向鏈表(DbLinkList)實例詳解）文章只能為提供參考，不一定能成為您想要的結果。以下是C#數據構造之雙向鏈表(DbLinkList)實例詳解正文
本文實例講述了C#數據構造之雙向鏈表(DbLinkList)。分享給年夜家供年夜家參考，詳細以下：
這是繼上一篇《C#數據構造之單鏈表(LinkList)實例詳解》的持續，關於雙向鏈接，節點上除Next屬性外，還要有Prev屬性用來指向前一個節點，DbNode界說以下：
namespace 線性表
{
public class DbNode<T>
{
private T data;
private DbNode<T> prev;
private DbNode<T> next;
public DbNode(T data, DbNode<T> next,DbNode<T> prev)
{
this.data = data;
this.next = next;
this.prev = prev;
}
public DbNode(T data, DbNode<T> next)
{
this.data = data;
this.next = next;
this.prev = null;
}
public DbNode(DbNode<T> next)
{
this.data = default(T);
this.next = next;
this.prev = null;
}
public DbNode(T data)
{
this.data = data;
this.next = null;
this.prev = null;
}
public DbNode()
{
data = default(T);
next = null;
prev = null;
}
public T Data
{
set { this.data = value; }
get { return this.data; }
}
public DbNode<T> Prev
{
get { return prev; }
set { prev = value; }
}
public DbNode<T> Next
{
get { return next; }
set { next = value; }
}
}
}
雙鏈表的拔出操作要略微龐雜一點，表示圖以下：
異樣關於刪除操作，也要額定處置prev指向
完全完成DbLinkList<T>：
using System;
using System.Text;
namespace 線性表
{
public class DbLinkList<T> : IListDS<T>
{
private DbNode<T> head;
public DbNode<T> Head
{
get { return head; }
set { head = value; }
}
public DbLinkList()
{
head = null;
}
/// <summary>
/// 類索引器
/// </summary>
/// <param name="index"></param>
/// <returns></returns>
public T this[int index]
{
get
{
return this.GetItemAt(index);
}
}
/// <summary>
/// 前往單鏈表的長度
/// </summary>
/// <returns></returns>
public int Count()
{
DbNode<T> p = head;
int len = 0;
while (p != null)
{
len++;
p = p.Next;
}
return len;
}
/// <summary>
/// 清空
/// </summary>
public void Clear()
{
head = null;
}
/// <summary>
/// 能否為空
/// </summary>
/// <returns></returns>
public bool IsEmpty()
{
return head == null;
}
/// <summary>
/// 在最初附加元素
/// </summary>
/// <param name="item"></param>
public void Append(T item)
{
DbNode<T> d = new DbNode<T>(item);
DbNode<T> n = new DbNode<T>();
if (head == null)
{
head = d;
return;
}
n = head;
while (n.Next != null)
{
n = n.Next;
}
n.Next = d;
d.Prev = n;
}
//前插
public void InsertBefore(T item, int i)
{
if (IsEmpty() || i < 0)
{
Console.WriteLine("List is empty or Position is error!");
return;
}
//在最開首拔出
if (i == 0)
{
DbNode<T> q = new DbNode<T>(item);
q.Next = head;//把"頭"改成第二個元素
head.Prev = q;
head = q;//把本身設置為"頭"
return;
}
DbNode<T> n = head;
DbNode<T> d = new DbNode<T>();
int j = 0;
//找到地位i的前一個元素d
while (n.Next != null && j < i)
{
d = n;
n = n.Next;
j++;
}
if (n.Next == null) //解釋是在最初節點拔出(即追加)
{
DbNode<T> q = new DbNode<T>(item);
n.Next = q;
q.Prev = n;
q.Next = null;
}
else
{
if (j == i)
{
DbNode<T> q = new DbNode<T>(item);
d.Next = q;
q.Prev = d;
q.Next = n;
n.Prev = q;
}
}
}
/// <summary>
/// 在地位i後拔出元素item
/// </summary>
/// <param name="item"></param>
/// <param name="i"></param>
public void InsertAfter(T item, int i)
{
if (IsEmpty() || i < 0)
{
Console.WriteLine("List is empty or Position is error!");
return;
}
if (i == 0)
{
DbNode<T> q = new DbNode<T>(item);
q.Next = head.Next;
head.Next.Prev = q;
head.Next = q;
q.Prev = head;
return;
}
DbNode<T> p = head;
int j = 0;
while (p != null && j < i)
{
p = p.Next;
j++;
}
if (j == i)
{
DbNode<T> q = new DbNode<T>(item);
q.Next = p.Next;
if (p.Next != null)
{
p.Next.Prev = q;
}
p.Next = q;
q.Prev = p;
}
else
{
Console.WriteLine("Position is error!");
}
}
/// <summary>
/// 刪除地位i的元素
/// </summary>
/// <param name="i"></param>
/// <returns></returns>
public T RemoveAt(int i)
{
if (IsEmpty() || i < 0)
{
Console.WriteLine("Link is empty or Position is error!");
return default(T);
}
DbNode<T> q = new DbNode<T>();
if (i == 0)
{
q = head;
head = head.Next;
head.Prev = null;
return q.Data;
}
DbNode<T> p = head;
int j = 0;
while (p.Next != null && j < i)
{
j++;
q = p;
p = p.Next;
}
if (j == i)
{
p.Next.Prev = q;
q.Next = p.Next;
return p.Data;
}
else
{
Console.WriteLine("The node is not exist!");
return default(T);
}
}
/// <summary>
/// 獲得指定地位的元素
/// </summary>
/// <param name="i"></param>
/// <returns></returns>
public T GetItemAt(int i)
{
if (IsEmpty())
{
Console.WriteLine("List is empty!");
return default(T);
}
DbNode<T> p = new DbNode<T>();
p = head;
if (i == 0)
{
return p.Data;
}
int j = 0;
while (p.Next != null && j < i)
{
j++;
p = p.Next;
}
if (j == i)
{
return p.Data;
}
else
{
Console.WriteLine("The node is not exist!");
return default(T);
}
}
//按元素值查找索引
public int IndexOf(T value)
{
if (IsEmpty())
{
Console.WriteLine("List is Empty!");
return -1;
}
DbNode<T> p = new DbNode<T>();
p = head;
int i = 0;
while (!p.Data.Equals(value) && p.Next != null)
{
p = p.Next;
i++;
}
return i;
}
/// <summary>
/// 元素反轉
/// </summary>
public void Reverse()
{
DbLinkList<T> result = new DbLinkList<T>();
DbNode<T> t = this.head;
result.Head = new DbNode<T>(t.Data);
t = t.Next;
//(把以後鏈接的元素從head開端遍歷，逐一拔出到另外一個空鏈表中，如許獲得的新鏈表正好元素次序跟原鏈表是相反的)
while (t!=null)
{
result.InsertBefore(t.Data, 0);
t = t.Next;
}
this.head = result.head;//將原鏈表直接掛到"反轉後的鏈表"上
result = null;//顯式清空原鏈表的援用，以便讓GC能直接收受接管
}
//獲得某個指定的節點(為了上面測試從後向前遍歷)
private DbNode<T> GetNodeAt(int i){
if (IsEmpty())
{
Console.WriteLine("List is empty!");
return null;
}
DbNode<T> p = new DbNode<T>();
p = head;
if (i == 0)
{
return p;
}
int j = 0;
while (p.Next != null && j < i)
{
j++;
p = p.Next;
}
if (j == i)
{
return p;
}
else
{
Console.WriteLine("The node is not exist!");
return null;
}
}
/// <summary>
/// 測試用prev屬性從前面開端遍歷
/// </summary>
/// <returns></returns>
public string TestPrevErgodic()
{
DbNode<T> tail = GetNodeAt(Count() - 1);
StringBuilder sb = new StringBuilder();
sb.Append(tail.Data.ToString() + ",");
while (tail.Prev != null)
{
sb.Append(tail.Prev.Data.ToString() + ",");
tail = tail.Prev;
}
return sb.ToString().TrimEnd(',');
}
public override string ToString()
{
StringBuilder sb = new StringBuilder();
DbNode<T> n = this.head;
sb.Append(n.Data.ToString() + ",");
while (n.Next != null)
{
sb.Append(n.Next.Data.ToString() + ",");
n = n.Next;
}
return sb.ToString().TrimEnd(',');
}
}
}
測試代碼片斷：
Console.WriteLine("-------------------------------------");
Console.WriteLine("雙鏈表測試開端...");
DbLinkList<string> dblink = new DbLinkList<string>();
dblink.Head = new DbNode<string>("x");
dblink.InsertBefore("w", 0);
dblink.InsertBefore("v", 0);
dblink.Append("y");
dblink.InsertBefore("z", dblink.Count());
Console.WriteLine(dblink.Count());//5
Console.WriteLine(dblink.ToString());//v,w,x,y,z
Console.WriteLine(dblink[1]);//w
Console.WriteLine(dblink[0]);//v
Console.WriteLine(dblink[4]);//z
Console.WriteLine(dblink.IndexOf("z"));//4
Console.WriteLine(dblink.RemoveAt(2));//x
Console.WriteLine(dblink.ToString());//v,w,y,z
dblink.InsertBefore("x", 2);
Console.WriteLine(dblink.ToString());//v,w,x,y,z
Console.WriteLine(dblink.GetItemAt(2));//x
dblink.Reverse();
Console.WriteLine(dblink.ToString());//z,y,x,w,v
dblink.InsertAfter("1", 0);
dblink.InsertAfter("2", 1);
dblink.InsertAfter("6", 5);
dblink.InsertAfter("8", 7);
dblink.InsertAfter("A", 10);//Position is error!
Console.WriteLine(dblink.ToString()); //z,1,2,y,x,w,6,v,8
string _tail = dblink.GetItemAt(dblink.Count()-1);
Console.WriteLine(_tail);
Console.WriteLine(dblink.TestPrevErgodic());//8
Console.ReadKey(); //8,v,6,w,x,y,2,1,z
固然從下面的測試代碼中，仿佛其實不能看出雙鏈表的長處，雙鏈表的利益在於，假如須要在鏈表中，須要經由過程某個節點獲得它的先驅節點時，雙鏈表直接用prev屬性就可以找到；而單鏈表要做到這一點，必需再次從Head節點開端一個一個用Next向下找，如許時光龐雜度從O(n)降到O(1)，明顯更有用率。
注：假如把雙鏈表再做一下改革，讓頭尾接起來，即Head的Prev屬性指向最初一個節點(就叫做Tail吧)，同時把Tail節點的Next屬性指向Head節點，就構成了所謂的“輪回雙向鏈表”
固然，如許的構造可以在鏈表中再增長一個Tail節點屬性，在做元素拔出或刪除時，可以輪回究竟以更新尾節點Tail(固然如許會給拔出/刪除元素帶來一些額定的開支)，然則卻可以給GetItemAt(int i)辦法帶來優化的空間，好比要查找的元素在前半段時，可以從Head開端用next向後找；反之，假如要找的元素在後半段，則可以從Tail節點用prev屬性向前找。
注：.Net中微軟曾經給出了一個內置的雙向鏈表System.Collections.Generic.LinkedList<T>，在懂得雙鏈表的道理後，建議年夜家直接體系內置的鏈表。
願望本文所述對年夜家C#法式設計有所贊助。
