C++ 实现模板类Stack

　　Fibonacci.h使用递归方法实现斐波那契数列函数。Stack.h，定义一个Stack模板类，接收任意类型，模拟栈的使用，内部使用一个数组，通过size和capacity不断根据输入的多寡增容或缩小数组，实现push函数，压入数据到栈中，以及top函数，查看栈顶数据，pop函数，弹出栈顶数组。

#pragma once

unsigned int Fibonacci(unsigned int n)
{
    if (n == 0)
    {
        return 0;
    }
    else if (n == 1 || n == 2)
    {
        return 1;
    }
    else
    {
        return Fibonacci(n - 1) + Fibonacci(n - 2);
    }
}

#pragma once
#include <iostream>

using namespace std;

template <typename T>
class Stack
{
private:
    size_t capacity;    // 可容纳对象数量
    size_t size;        // 大小，存储对象数量
    size_t ptr;            // 栈顶索引
    T *arr;                // 数组指针
public:
    Stack() {
        capacity = 2;
        size = 0;
        ptr = -1;
        arr = new T[capacity];
    }
    ~Stack() {
        delete[]arr;
    }

    size_t Size() { return this->size; }
    size_t Capacity() { return this->capacity; }

    void push(const T&);
    void pop();
    T top() const;
    bool empty() const {
        return size == 0 ? true : false;
    }
};

template <typename T>
void Stack<T>::push(const T& elem)
{
    // 如果数组已满，扩容
    if (size == capacity) {
        T *tmp = arr;
        capacity *= 2;
        arr = new T[capacity];
        memcpy(arr, tmp, sizeof(T) * size);
        delete[]tmp;
    }
    ++ptr;
    arr[ptr] = elem;
    ++size;
}

template <typename T>
void Stack<T>::pop()
{
    if (this->empty()) {
        throw out_of_range("Stack<>::pop(): Stack is empty");
    }
    --ptr;
    --size;
    // 如果数组capacity比size的四倍还大，缩小数组大小
    if (capacity >= size * 4 && size != 0)
    {
        T *tmp = arr;
        capacity = size * 2;
        arr = new T[capacity];
        memcpy(arr, tmp, sizeof(T) * size);
        delete[]tmp;
    }
}

template <typename T>
T Stack<T>::top() const
{
    if (empty()) {
        throw out_of_range("Stack<>::pop(): Stack is empty");
    }
    T elem = arr[ptr];
    return elem;
}

#include <iostream>
#include <string>
#include "Stack.h"
#include "Fibonacci.h"

using namespace std;

void test1()
{
    // 测试Stack实现栈类
    try {
        Stack<int> ms;
        for (int i = 0; i < 8; ++i)
        {
            ms.push(Fibonacci(i));
        }
        cout << "size: " << ms.Size() << "; capacity: " << ms.Capacity() << "; empty? " << ms.empty() << endl;
        for (int i = 0; i < 6; ++i) 
        {
            cout << ms.top() << endl;
            ms.pop();
        }
        cout << "size: " << ms.Size() << "; capacity: " << ms.Capacity() << "; empty? " << ms.empty() << endl;
        cout << ms.top() << endl;
        ms.pop();
        cout << ms.top() << endl;
        ms.pop();
        cout << "size: " << ms.Size() << "; capacity: " << ms.Capacity() << "; empty? " << ms.empty() << endl;
    }
    catch (const exception& e) {
        cout << e.what() << endl;
    }
}

void test2()
{
    // 测试Stack实现栈类
    try {
        Stack<string> ms;
        ms.push("Hello, world!");
        ms.push("你好，世界！");
        cout << "size: " << ms.Size() << "; capacity: " << ms.Capacity() << "; empty? " << ms.empty() << endl;
        cout << ms.top() << endl;
        ms.pop();
        cout << ms.top() << endl;
        ms.pop();
        ms.pop();
    }
    catch (const exception& e) {
        cout << e.what() << endl;
    }
}

int main()
{
    test1();
    test2();

    return 0;
}