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数据结构C#版笔记--堆栈(Stack)

 

堆栈(Stack)最明显的特征就是“先进后出”，本质上讲堆栈也是一种线性结构，符合线性结构的基本特点：即每个节点有且只有一个前驱节点和一个后续节点。

相对前面学习过的顺序表、链表不同的地方在于：Stack把所有操作限制在"只能在线性结构的某一端"进行，而不能在中间插入或删除元素。下面是示意图：

从示意图中可以看出，堆栈有二种实现方式：基于数组的顺序堆栈实现、类似链表的链式堆栈实现

先抽象堆栈的接口IStack:

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namespace 栈与队列 {     public interface IStack<T>     {         /// <summary>         /// 返回堆栈的实际元素个数         /// </summary>         /// <returns></returns>         int Count();           /// <summary>         /// 判断堆栈是否为空         /// </summary>         /// <returns></returns>         bool IsEmpty();           /// <summary>         /// 清空堆栈里的元素         /// </summary>         void Clear();           /// <summary>         /// 入栈：将元素压入堆栈中         /// </summary>         /// <param name="item"></param>         void Push(T item);           /// <summary>         /// 出栈：从堆栈顶取一个元素，并从堆栈中删除         /// </summary>         /// <returns></returns>         T Pop();           /// <summary>         /// 取堆栈顶部的元素(但不删除)         /// </summary>         /// <returns></returns>         T Peek();     } }

顺序堆栈(SeqStack)的实现：

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using System; using System.Text;   namespace 栈与队列 {     public class SeqStack<T>:IStack<T>     {         private int maxsize;         private T[] data;         private int top;                    public SeqStack(int size)         {             data = new T[size];             maxsize = size;             top = -1;         }           #region //接口实现部分         public int Count()         {             return top + 1;         }           public void Clear()         {             top = -1;         }           public bool IsEmpty()         {             return top == -1;         }           public void Push(T item)         {             if (IsFull())             {                 Console.WriteLine("Stack is full");                 return;             }             data[++top] = item;         }             public T Pop()         {             T tmp = default(T);             if (IsEmpty())             {                 Console.WriteLine("Stack is empty");                 return tmp;             }             tmp = data[top];             top--;             return tmp;         }           public T Peek()         {             if (IsEmpty())             {                 Console.WriteLine("Stack is empty!");                 return default(T);             }             return data[top];         }         #endregion           public bool IsFull()         {             return top == maxsize - 1;         }             public override string ToString()         {             StringBuilder sb = new StringBuilder();             for (int i = top;i>=0;i--)             {                 sb.Append(data[i] + ",");             }             return sb.ToString().Trim(',');         }              } }

链式堆栈(LinkStack)的实现

先定义节点Node.cs

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namespace 栈与队列 {     public class Node<T>     {         private T data;           private Node<T> next;           public Node(T data, Node<T> next)         {             this.data = data;             this.next = next;         }           public Node(Node<T> next)         {             this.next = next;             this.data = default(T);                       }           public Node(T data)         {             this.data = data;             this.next = null;         }           public Node()         {             this.data = default(T);             this.next = null;         }           public T Data {             get { return this.data; }             set { this.data = value; }         }           public Node<T> Next         {             get { return next; }             set { next = value; }         }     } }

下面是LinkStack.cs

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using System; using System.Text;   namespace 栈与队列 {     public class LinkStack<T>:IStack<T>     {           private Node<T> top;         private int num;//节点个数               /// <summary>         /// 顶部节点         /// </summary>         public Node<T> Top         {             get { return top; }             set { top = value; }         }                    public LinkStack()         {             top = null;             num = 0;         }           public int Count()         {             return num;         }           public void Clear()         {             top = null;             num = 0;         }           public bool IsEmpty()         {             if (top == null && num == 0)             {                 return true;             }             else             {                 return false;             }         }           public void Push(T item)         {             Node<T> q = new Node<T>(item);             if (top == null)             {                 top = q;             }             else             {                 q.Next = top;                 top = q;             }             num++;         }           public T Pop()         {             if (IsEmpty())             {                 Console.WriteLine("Stack is empty!");                 return default(T);             }             Node<T> p = top;             top = top.Next;             num--;               return p.Data;         }           public T Peek()         {             if (IsEmpty())             {                 Console.WriteLine("Stack is empty!");                 return default(T);             }             return top.Data;         }             public override string ToString()         {             StringBuilder sb = new StringBuilder();             if (top != null)             {                 sb.Append(top.Data.ToString() + ",");                 Node<T> p = top;                 while (p.Next != null)                 {                                        sb.Append(p.Next.Data.ToString()+ ",");                     p = p.Next;                 }             }               return sb.ToString();         }     } }

测试代码片段：

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Console.WriteLine("顺序堆栈测试开始..."); SeqStack<int> seqStack = new SeqStack<int>(10); seqStack.Push(1); seqStack.Push(2); seqStack.Push(3);   Console.WriteLine(seqStack); Console.WriteLine(seqStack.Peek()); Console.WriteLine(seqStack); Console.WriteLine(seqStack.Pop()); Console.WriteLine(seqStack);   Console.WriteLine("链堆栈测试开始..."); LinkStack<int> linkStack = new LinkStack<int>(); linkStack.Push(1); linkStack.Push(2); linkStack.Push(3);   Console.WriteLine(linkStack); Console.WriteLine(linkStack.Peek()); Console.WriteLine(linkStack); Console.WriteLine(linkStack.Pop()); Console.WriteLine(linkStack);   Console.ReadLine();

.Net中System.Collections.Generic.Stack<T>已经提供了堆栈的基本实现，明白原理后，仍然推荐大家使用内置的实现。

作者：菩提树下的杨过
出处：http://yjmyzz.cnblogs.com 
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