基本数据结构：栈

堆栈（英语：stack），也可直接称栈。在计算机科学中，是一种特殊的串行形式的数据结构，它的特殊之处在于只能允许在链结串行或阵列的一端（称为堆栈顶端指标，英语：top）进行加入资料（英语：push）和输出资料（英语：pop）的运算。另外堆栈也可以用一维阵列或连结串行的形式来完成。堆栈的另外一个相对的操作方式称为伫列。

由于堆栈数据结构只允许在一端进行操作，因而按照后进先出（LIFO, Last In First Out）的原理运作。

堆栈数据结构使用两种基本操作：推入（push）和弹出（pop）：

• 推入：将数据放入堆栈的顶端（阵列形式或串行形式），堆栈顶端top指标加一。
• 弹出：将顶端数据资料输出（回传），堆栈顶端资料减一。

一个栈的简单实现如下：

#ifndef STACK_H
#define STACK_H
#include <iostream>
using std::ostream;

const int defaultSize = 5;
const int overSize = 2;
template <typename T>
class Stack
{

public:
	Stack(int size = defaultSize) : maxSize(size),top(-1)
	{
		elements = new T[size];//创建数组
	}

	~Stack()
	{
		delete []elements;
	}

	bool isFull() const
	{
		return top == (maxSize - 1);
	}

	bool isEmpty() const
	{
		return top == -1;
	}

	void makeEmpty()
	{
		top = -1;
	}

	int getSize() const
	{
		return top+1;
	}

	void push(T &value)
	{
		if(!isFull())
		{
			elements[++top] = value;
		}
		else//栈满
		{
			resize();
			elements[++top] = value;
		}
	}

	bool pop(T &t)
	{
		if(!isEmpty())
		{
			t = elements[top--];
			return true;
		}
		else//栈空
		{
			return false;
		}
	}

	bool getTop(T &t) const
	{
		if(!isEmpty())
		{
			t = elements[top];
			return true;
		}
		else//栈空
		{
			return false;
		}
	}

	friend ostream & operator<< (ostream &out,const Stack<T> &s)
	{
		out << "the stack top is " << s.top << endl;

		for(int i = 0; i <= s.top; i++)
		{
			cout <<" "<<s.elements[i] ;
		}
		out << endl;

		return out;
	}

private:
	T *elements;
	int top;
	int maxSize;

	void resize()//每次栈满后需对栈进行扩充 
	{
		T *newElements = new T[maxSize+overSize];
		for(int i = 0; i < maxSize;i++)
		{
			newElements[i] = elements[i];//拷贝原来的数据
		}

		maxSize += overSize;
		delete []elements;
		elements = newElements;
		
	}
};




#endif

测试代码如下：

#include "stack.h"
#include <fstream>
using std::cin;  
using std::cout;  
using std::endl;  

using std::ifstream;

int main()
{
	Stack<int> sta;
	ifstream fin("data.txt");
	
	int data;
	while (!fin.eof()){
		fin >> data;
		sta.push(data);		
	}
	cout << "The initial Stack in the file is:\n" << sta;
	cout << "The current size of the Stack is: " << sta.getSize() << endl;
	sta.getTop(data);
	cout << "The current Top element of the Stack is : " << data << endl;
	sta.pop(data);
	cout << "\nDo a Pop operation, then the stack is:\n" << sta << endl;
	cout << "The data popped is: " << data << endl;
	sta.getTop(data);
	cout << "The current Top element of the Stack is : " << data << endl;

	cout << "\nTest the state of the stack:\n";
	if (sta.isEmpty())	cout << "The stack is empty now!\n";
	else if (sta.isFull())	cout << "The stack is full now!\n";
	else	cout << "The stack is not empty and not full now!\n";
	cout << "Now make the stack empty, then the state of the stack is:\n";
	sta.makeEmpty();
	if (sta.isEmpty())	cout << "The stack is empty now!\n";
	else if (sta.isFull())	cout << "The stack is full now!\n";
	else	cout << "The stack is not empty and not full now!\n";

	system("pause");
	return 0;
}