Interview problem: Implement shared pointer

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template<typename T> class SharedPtr { public: explicit SharedPtr(T *ptr=nullptr): ptr_(ptr), count_(new long(0)) { if (ptr_) { ++(*count_); } } ~SharedPtr() { if (count_) { --(*count_); if (*count_ == 0) { delete count_; delete ptr_; } } } SharedPtr(const SharedPtr& other): ptr_(other.ptr_), count_(other.count_) { ++(*count_); } SharedPtr& operator=(const SharedPtr& other) { SharedPtr tmp(other); tmp.swap(*this); return *this; } SharedPtr(SharedPtr&& other) noexcept: ptr_(other.ptr_), count_(other.count_) { other.ptr_ = nullptr; other.count_ = nullptr; } SharedPtr& operator=(SharedPtr&& other) noexcept { other.swap(*this); return *this; } T& operator*() const { return *ptr_; } T* operator->() const { return ptr_; } explicit operator bool() const { return ptr_; } void swap(SharedPtr &other) noexcept { std::swap(ptr_, other.ptr_); std::swap(count_, other.count_); } private: T* ptr_; long *count_; };