C++复习之类模板

用模板来实现一个顺序栈//类模板

#include <iostream>
#include <cstring>

template<typename T>
class SeqStack//模板名称+类型参数列表 = 类名称
{
public:
    //构造与析构函数名不用加<T>,其他出现模板的地方都加上类型参数列表
    SeqStack(int size = 10)
        : _pstack(new T[size])
        , _top(-1)
        , _size(size)
    { }
    ~SeqStack()
    {
        delete[]_pstack;
        _pstack = nullptr;
    }
    SeqStack(const SeqStack<T> &src)
        : _top(src._top)
        , _size(src._size)
    {
        _pstack = new T[src._size];
        for (int i = 0; i <= _top; ++i)
        {
            _pstack[i] = src._pstack[i];
        }
    }
    SeqStack<T>& operator=(const SeqStack<T> &src)
    {
        if (this == &src)
        {
            return *this;
        }
        delete[]_pstack;
        _top = src._top;
        _size = src._size;
        _pstack = new T[_size];
        for (int i = 0; i <= _top; ++i)
        {
            _pstack[i] = src._pstack[i];
        }
        return *this;
    }
    void push(const T &val);//入栈操作，类外实现

    void pop()
    {
        if (empty())
        {
            return;
        }
        --_top;
    }
    T top()const
    {
        if (empty())
        {
            throw "stack is empty!";
        }
        return _pstack[_top];
    }
    bool full()const
    {
        return _top == size - 1;
    }
    bool empty()const
    {
        return _top = -1;
    }
private:
    T* _pstack;
    int _top;
    int _size;
    //顺序栈底层数组二倍方式进行扩容
    void resize()
    {
        T *ptmp = new T[2 * _size];
        for (int i = 0; i <= _top; ++i)
        {
            ptmp[i] = _pstack[i];
        }
        delete[]_pstack;
        _pstack = ptmp;
        _size *= 2;
    }
};  
template<typename T>
void SeqStack<T>:: push(const T &val)
{
    if (full())
    {
        resize();
    }
    _pstack[++_top] = val;
}

int main()
{
    //类模板的选择性实例化
    SeqStack<int> s1;//用整型实例化类模板
    //class SeqStack<int>{ };模板类
    s1.push(20);
    s1.push(78);
    s1.push(32);
    s1.push(56);
    s1.pop();
    cout << s1.top() << endl;
    return 0;
}