Unique Buffer

Implementing the copy-and-swap idiom for resource ownership in C++

This medium-difficulty C++ problem tests whether you understand the mechanics of resource ownership and the copy-and-swap pattern — a design technique that simplifies the tricky interactions between copy construction, move construction, assignment, and destruction. It's the kind of question trading firms and systems-software shops use to filter candidates who can write exception-safe, non-buggy resource-management code.

The core challenge is implementing each of the four special member functions (copy constructor, move constructor, assignment operator, destructor) correctly so that ownership semantics are unambiguous and self-assignment doesn't corrupt the object. The copy-and-swap idiom sidesteps the complexity of writing separate copy-assignment and move-assignment operators by collapsing them into a single by-value assignment that delegates to swap. Correctness depends on getting the interaction between move semantics, the non-throwing swap, and the temporary parameter right.

• Rule of Five: copy constructor, move constructor, copy-assignment, move-assignment, destructor
• Move semantics and ownership transfer
• Exception safety guarantees (strong guarantee via copy-and-swap)
• Bounds checking and exception throwing