#include <iostream>

using namespace std;
template<class T>
class SmartPtr{
public:
    explicit SmartPtr():ptr(nullptr), count(new int(0)){}
    explicit SmartPtr(T* p):ptr(p), count(new int(0)){
        *count = 1;
    }
    ~SmartPtr(){
        --(*count);
        if(*count == 0){
            delete(count);
            delete(ptr);
            count = nullptr;
            ptr = nullptr;
        }
    }
    //拷贝构造
    SmartPtr(const SmartPtr<T> &other){
        count = other.count;
        ptr = other.ptr;
        ++(*count);
    }
    SmartPtr& operator= (const SmartPtr<T> &other){
        count = other.count;
        ptr = other.ptr;
        ++(*count);
        return (*this);
    }
    T& operator*(){
        return *ptr;
    }
    T* operator->(){
        return ptr;
    }
    void swap(SmartPtr<T> other){
        std::swap(*this, other);
    }
    void use_count(){
        cout<<(*count)<<endl;
    }
private:
    T *ptr;
    int* count{};
};


int main() {

    SmartPtr<int> ptr1(new int(1));
    ptr1.use_count();
    SmartPtr<int> ptr2(ptr1);
    ptr1.use_count();
    ptr2.use_count();
    SmartPtr<int> ptr3 = ptr2;
    ptr1.use_count();
    ptr2.use_count();
    ptr3.use_count();

    return 0;
}