Implement a reference-counted smart pointer

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.

Reference-Counted Smart Pointer Lifecycle

Simulate SharedPtr ownership operations and return use_count/get query outputs.

Examples

Example 1

Input: ((('new', 'a', 'obj'), ('copy', 'b', 'a'), ('use_count', 'a'), ('reset', 'a'), ('use_count', 'b')),)
Output: [2, 1]

Explanation: Copy increments and reset decrements.

Example 2

Input: ((('new', 'a', 'x'), ('move', 'b', 'a'), ('get', 'a'), ('use_count', 'b')),)
Output: [None, 1]

Explanation: Move leaves source null.

Hints

1. A real C++ implementation stores a control block with pointer and count, incrementing on copy and decrementing on destruction/reset.