算法系列15天速成 第十天 栈
一： 概念
栈，同样是一种特殊的线性表，是一种Last In First Out（LIFO)的形式，现实中有很多这样的例子，
比如：食堂中的一叠盘子，我们只能从顶端一个一个的取。
二：存储结构
”栈“不像”队列“，需要两个指针来维护，栈只需要一个指针就够了，这得益于栈是一种一端受限的线性表。
这里同样用”顺序结构“来存储这个”栈“，top指针指向栈顶，所有的操作只能在top处。
代码段：
#region 栈的数据结构
/// <summary>
/// 栈的数据结构
/// </summary>
public class SeqStack<T>
{
public T[] data;
/// <summary>
/// 栈顶指针
/// </summary>
public int top = -1;
public SeqStack(int lenth)
{
data = new T[lenth];
}
}
#endregion
三：常用操作
栈的操作有：①初始化栈，②入栈，③出栈，④获取栈顶。
1: 初始化栈
这个还是比较简单的，初始化栈时，设置默认top指针为-1，这个就不用图来展示了。
代码段：
#region 栈的初始化操作
/// <summary>
/// 栈的初始化操作
/// </summary>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public SeqStack<T> SeqStackInit<T>(int length)
{
SeqStack<T> seqStack = new SeqStack<T>(length);
seqStack.top = -1;
return seqStack;
}
#endregion
2：入栈
这个操作主要就是做两件事情：① 将元素从栈顶压入，② top指针自增。
代码段：
#region 入栈
/// <summary>
/// 入栈
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="seqStack"></param>
/// <param name="data"></param>
public void SeqStackPush<T>(SeqStack<T> seqStack, T data)
{
if (SeqStackIsFull(seqStack))
throw new Exception("不好意思，栈溢出");
seqStack.data[++seqStack.top] = data;
}
#endregion
3：出栈
同样跟“入栈”类似，需要做两件事情，①干掉top处的元素，②top指针自减。
代码段
#region 出栈
/// <summary>
/// 出栈
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="seqStack"></param>
/// <returns></returns>
public T SeqStackPop<T>(SeqStack<T> seqStack)
{
if (SeqStackIsEmpty(seqStack))
throw new Exception("呜呜，栈已空");
seqStack.data[seqStack.top] = default(T);
return seqStack.data[--seqStack.top];
}
#endregion
4：获取栈顶元素
这个很简单，跟“出栈”唯一不同的是不破坏栈顶元素，只是翻出来看看而已。
代码段
#region 获取栈顶
/// <summary>
/// 获取栈顶
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="seqStack"></param>
/// <returns></returns>
public T SeqStackPeek<T>(SeqStack<T> seqStack)
{
if (SeqStackIsEmpty(seqStack))
throw new Exception("栈已空");
return seqStack.data[seqStack.top];
}
#endregion
总的运行代码如下
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace SeqStack
{
class Program
{
static void Main(string[] args)
{
SeqStackClass stackManager = new SeqStackClass();
SeqStack<Student> seqStack = stackManager.SeqStackInit<Student>(10);
Console.WriteLine("******************** 压入ID=1,ID=2,ID=3的元素 ***********************\n");
//压入ID=1,ID=2,ID=3的元素
stackManager.SeqStackPush(seqStack, new Student() { ID = 1, Name = "一线码农", Age = 23 });
stackManager.SeqStackPush(seqStack, new Student() { ID = 2, Name = "huangxincheng520", Age = 23 });
stackManager.SeqStackPush(seqStack, new Student() { ID = 3, Name = "51cto", Age = 23 });
Console.WriteLine(".... 压入成功，当前栈中元素有：" + stackManager.SeqStackLen(seqStack) + "个");
Console.WriteLine("\n****************** 查看栈顶元素 ********************");
var result = stackManager.SeqStackPeek(seqStack);
Console.WriteLine("栈顶元素为：ID=" + result.ID + ",Name=" + result.Name + ",Age=" + result.Age);
Console.WriteLine("\n******************** 弹出栈顶元素 ***********************");
stackManager.SeqStackPop(seqStack);
Console.WriteLine("\n****************** 查看栈中的元素 ********************");
for (int i = 0; i < stackManager.SeqStackLen(seqStack); i++)
{
Console.WriteLine("栈顶元素为：ID=" + seqStack.data[i].ID + ",Name=" + seqStack.data[i].Name + ",Age=" + seqStack.data[i].Age);
}
Console.Read();
}
}
#region 学生数据实体
/// <summary>
/// 学生数据实体
/// </summary>
public class Student
{
public int ID { get; set; }
public string Name { get; set; }
public int Age { get; set; }
}
#endregion
#region 栈的数据结构
/// <summary>
/// 栈的数据结构
/// </summary>
public class SeqStack<T>
{
public T[] data;
/// <summary>
/// 栈顶指针
/// </summary>
public int top = -1;
public SeqStack(int lenth)
{
data = new T[lenth];
}
}
#endregion
public class SeqStackClass
{
#region 栈的初始化操作
/// <summary>
/// 栈的初始化操作
/// </summary>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public SeqStack<T> SeqStackInit<T>(int length)
{
SeqStack<T> seqStack = new SeqStack<T>(length);
seqStack.top = -1;
return seqStack;
}
#endregion
#region 判断栈是否为空
/// <summary>
/// 判断栈是否为空
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="seqStack"></param>
/// <returns></returns>
public bool SeqStackIsEmpty<T>(SeqStack<T> seqStack)
{
return seqStack.top == -1;
}
#endregion
#region 清空栈
/// <summary>
/// 清空栈
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="seqStack"></param>
public void SeqStackClear<T>(SeqStack<T> seqStack)
{
seqStack.top = -1;
}
#endregion
#region 栈是否已满
/// <summary>
/// 栈是否已满
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="seqStack"></param>
public bool SeqStackIsFull<T>(SeqStack<T> seqStack)
{
return seqStack.top == seqStack.data.Length;
}
#endregion
#region 入栈
/// <summary>
/// 入栈
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="seqStack"></param>
/// <param name="data"></param>
public void SeqStackPush<T>(SeqStack<T> seqStack, T data)
{
if (SeqStackIsFull(seqStack))
throw new Exception("不好意思，栈溢出");
seqStack.data[++seqStack.top] = data;
}
#endregion
#region 出栈
/// <summary>
/// 出栈
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="seqStack"></param>
/// <returns></returns>
public T SeqStackPop<T>(SeqStack<T> seqStack)
{
if (SeqStackIsEmpty(seqStack))
throw new Exception("呜呜，栈已空");
seqStack.data[seqStack.top] = default(T);
return seqStack.data[--seqStack.top];
}
#endregion
#region 获取栈顶
/// <summary>
/// 获取栈顶
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="seqStack"></param>
/// <returns></returns>
public T SeqStackPeek<T>(SeqStack<T> seqStack)
{
if (SeqStackIsEmpty(seqStack))
throw new Exception("栈已空");
return seqStack.data[seqStack.top];
}
#endregion
#region 获取栈中元素个数
/// <summary>
/// 获取栈中元素个数
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="seqStack"></param>
/// <returns></returns>
public int SeqStackLen<T>(SeqStack<T> seqStack)
{
return seqStack.top + 1;
}
#endregion
}
}