手撕智能指针，emmmmm
show me the code

#include <iostream>
using namespace std;

template<typename T>
class smartPtr {
private:
	T* _ptr;
	int* _count;
public:
	smartPtr(T* ptr = nullptr) :_ptr(ptr), _count(new int(1)) {
		cout << "Constructor is called!" << endl;
	}
	smartPtr(const smartPtr<T>& ptr) :_ptr(ptr._ptr), _count(ptr._count) {
		++(*_count);
		cout << "Copy constructor is called!" << endl;
	}
	smartPtr<T>& operator=(const smartPtr<T>& ptr){
		++(*ptr._count);	//防止自赋值带来的提前释放
		if (--(*_count) == 0) {
			delete _count;
			delete _ptr;
			cout << "original object  is deleted!" << endl;
		}
		_ptr = ptr._ptr;
		_count = ptr._count;
		cout << "Assignment operator overloaded is called!" << endl;
		return *this;
	}
	~smartPtr() {
		if (--(*_count) == 0) {
			delete _ptr;
			delete _count;
			_ptr = nullptr;
			_count = nullptr;
			cout << "Destructor is called!" << endl;
		}
	}
};

int main()
{
	// Test Constructor and Assignment Operator Overloaded
	smartPtr<int> p1(new int(0));
	p1 = p1;
	// Test Copy Constructor
	smartPtr<int> p2(p1);
	// Test Assignment Operator Overloaded
	smartPtr<int> p3(new int(1));
	p3 = p1;

	return 0;
}