Implement a reference-counted smart pointer
Company: Aurora
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: hard
Interview Round: Technical Screen
Implement a minimal C++ reference-counted smart pointer similar to `std::shared_ptr`.
Requirements:
- Create a class template `SharedPtr<T>` that manages a heap-allocated `T*`.
- Use RAII: the managed object must be deleted exactly once when the last `SharedPtr` owning it is destroyed.
- Support:
- Default constructor (null pointer)
- Constructor from raw pointer `T*`
- Destructor
- Copy constructor / copy assignment (increase reference count)
- Move constructor / move assignment (transfer ownership, leaving the source null)
- `T& operator*()`, `T* operator->()`, `T* get() const`
- `size_t use_count() const`
- `void reset(T* p = nullptr)`
- Handle self-assignment correctly and avoid memory leaks/double-free.
You may ignore thread-safety unless you explicitly choose to support it.
Quick Answer: This question evaluates understanding of C++ resource management, ownership semantics, RAII, and reference counting implementation within the coding and algorithms domain, emphasizing pointer semantics and object lifetime.
Simulate SharedPtr ownership operations and return use_count/get query outputs.
Examples
Input: ((('new', 'a', 'obj'), ('copy', 'b', 'a'), ('use_count', 'a'), ('reset', 'a'), ('use_count', 'b')),)
Expected Output: [2, 1]
Explanation: Copy increments and reset decrements.
Input: ((('new', 'a', 'x'), ('move', 'b', 'a'), ('get', 'a'), ('use_count', 'b')),)
Expected Output: [None, 1]
Explanation: Move leaves source null.
Hints
- A real C++ implementation stores a control block with pointer and count, incrementing on copy and decrementing on destruction/reset.