auto_ptr和shared_ptr

template<class T>
class auto_ptr
{
private:
    T *ap;
public:
    explicit auto_ptr(T *ptr = 0):ap(ptr){}
    ~auto_ptr(){delete ap;}
    auto_ptr(auto_ptr &rhs):ap(rhs.release()){}
    auto_ptr& operator=(auto_ptr &rhs)
    {
        reset(rhs.release());
        return *this;
    }
    T* operator*() const {return *ap;}
    T* operator->() const {return ap;}
    T* get() const {return ap;}
    T* release()
    {
        T *tmp = ap;
        ap = 0;
        return tmp;
    }
    void reset(T *ptr = 0)
    {
        if (ptr != ap)
        {
            delete ap;
            ap = ptr;
        }
    }
};