摸鱼的一天。。

\(shared\_ptr\) 指针的实现

template<typename T> class Shared_ptr {
private:
    T *ptr;
    int *use_count; // 用指针保证指向同一块地址
public:
    Shared_ptr() {
        ptr = nullptr;
        use_count = nullptr;
        cout << "Created" << endl;
    }
    Shared_ptr(T *p){
        ptr = p;
        use_count = new int(1);
        cout << "Created" << endl;
    }
    Shared_ptr(const Shared_ptr<T> &other) {
        ptr = other.ptr;
        ++(*other.use_count);
        use_count = other.use_count;
        cout << "Created" << endl;
    }
    Shared_ptr<T> operator=(const Shared_ptr &other) {
        if(this == &other)  return *this;
        (*other.use_count)++;
        if(ptr && --(*use_count) == 0) {
            delete ptr;
            delete use_count;
        }
        ptr = other.ptr;
        use_count = other.use_count;
        return *this;
    }
    T& operator*() {    // 返回指针的引用
        return *ptr;
    }
    T* operator->() {
        return ptr;
    }
    int get_use_count() {
        if(use_count == nullptr)    return 0;
        return *use_count;
    }
    ~Shared_ptr() {
        if(ptr && --(*use_count) == 0) {
            delete ptr;
            delete use_count;
            cout << "Destroy" << endl;
        }
    }
};