#include using namespace std; template class my_shared_ptr { public: my_shared_ptr(T* ptr = nullptr); ~my_shared_ptr(); my_shared_ptr(my_shared_ptr& pOther); my_shared_ptr& operator=(my_shared_ptr& pOther); long use_count() const; private: T* m_ptr; int* m_intCnt; }; template my_shared_ptr::my_shared_ptr(T* ptr) { if (ptr == nullptr) { m_ptr = nullptr; m_intCnt = nullptr; return; } m_intCnt = new int(1); m_ptr = ptr; } template my_shared_ptr::my_shared_ptr(my_shared_ptr& pOther) { if (pOther.m_ptr == nullptr) { m_ptr = nullptr; m_intCnt = nullptr; return; } ++(*pOther.m_intCnt); m_ptr = pOther.m_ptr; m_intCnt = pOther.m_intCnt; } template my_shared_ptr& my_shared_ptr::operator=(my_shared_ptr& pOther) { if (pOther.m_ptr == nullptr) { m_ptr = nullptr; m_intCnt = nullptr; return *this; } ++(*pOther.m_intCnt); m_ptr = pOther.m_ptr; m_intCnt = pOther.m_intCnt; return *this; } template my_shared_ptr::~my_shared_ptr() { if (m_ptr == nullptr || m_intCnt == nullptr) return; --(*m_intCnt); if (*m_intCnt == 0) { delete m_ptr; m_ptr = nullptr; delete m_intCnt; m_intCnt = nullptr; } } template long my_shared_ptr::use_count() const { if (m_ptr == nullptr || m_intCnt == nullptr) return 0; return *m_intCnt; } void Trial1() { my_shared_ptr ptr1(new int); cout << ptr1.use_count() << endl; my_shared_ptr ptr2(ptr1); cout << ptr1.use_count() << endl; my_shared_ptr ptr3; ptr3 = ptr1; cout << ptr1.use_count() << endl; cout << endl << endl; } void Trial2() { my_shared_ptr ptr1(new int); cout << ptr1.use_count() << endl; my_shared_ptr ptr3; ptr1 = ptr3; cout << ptr1.use_count() << endl; cout << endl << endl; } int main() { Trial1(); Trial2(); const my_shared_ptr ptr1(new int); cout << ptr1.use_count() << endl; my_shared_ptr ptr2(ptr1); return 0; }

Const Shared pointer copy