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This is a known ask for this company so I'd practiced it.
Start by clarifying the scope: a minimal unique_ptr that supports construction, destruction, move semantics, and basic access. Then implement the core members (pointer, destructor, move constructor/assignment, release, reset, get, operator*, operator->) while explaining design decisions and trade-offs. Finally, discuss extensions like custom deleters, array support, and comparison with std::unique_ptr.
Pro tip: Emphasize exception safety and the Rule of Five: explicitly delete copy operations and provide noexcept move operations. Mention that a unique_ptr should be as cheap as a raw pointer (zero overhead) and that the destructor must be noexcept.
Ask whether to implement a minimal version or full-featured (custom deleters, arrays). Confirm that move semantics and exclusive ownership are required.
Declare the template class with a pointer member. Delete copy constructor and copy assignment. Declare move constructor and move assignment as noexcept.
Write constructor (default and from raw pointer), destructor (delete pointer), move constructor (steal pointer, null out source), move assignment (release current, steal, null out source), and release/reset/get.
Implement operator* and operator->, bool conversion, and swap. Optionally add make_unique helper.
Talk about custom deleters (template parameter), array specialization (delete[]), and how std::unique_ptr handles these. Mention performance and exception safety.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Paired with the unique_ptr question in the same session.
Start by clarifying requirements (e.g., dynamic array, template/generic, exception safety) and then design the class with core operations: push_back, pop_back, operator[], size, capacity, and reserve. Implement with manual memory management, ensuring correct copy/move semantics and exception safety, and analyze time/space complexity.
Pro tip: Demonstrate production-quality thinking by discussing exception safety guarantees (e.g., strong guarantee for push_back) and move semantics to avoid unnecessary copies, which is crucial for performance-critical trading systems.
Ask about expected operations, type support (generic vs specific), memory constraints, and exception safety requirements. Confirm whether to mimic std::vector or a simplified version.
Define the public API (push_back, pop_back, operator[], size, capacity, reserve, etc.) and private members: pointer to data, size, capacity. Decide on growth strategy (e.g., doubling).
Write code for constructor, destructor, copy/move constructors and assignment operators, push_back, pop_back, reserve, and operator[]. Ensure proper memory allocation/deallocation and element construction/destruction.
Address self-assignment, empty vector operations, and exception safety (e.g., strong guarantee for push_back using copy-and-swap or careful ordering). Discuss move semantics for efficiency.
State time complexity for each operation (amortized O(1) for push_back, O(1) for pop_back and access) and space complexity. Mention testing strategies (unit tests, edge cases).
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Follow-up to the implementation questions.
Start by defining copy and move semantics in terms of resource ownership and performance. Explain how move semantics enables transfer of resources from temporary objects, avoiding deep copies, and highlight the impact on efficiency. Use a simple example to illustrate the difference and mention when each is used.
Pro tip: Emphasize that move semantics is not just about performance but also about correct resource management, especially in types that own resources like smart pointers or containers. Mention that understanding move semantics is crucial for writing exception-safe and efficient code in modern C++.
Explain that copy semantics creates a new object as a copy of an existing one, duplicating resources. This involves deep copies for resource-owning types, which can be expensive.
Explain that move semantics transfers resources from a source object (usually a temporary) to a new object, leaving the source in a valid but unspecified state. This avoids deep copies and improves performance.
Highlight that copy semantics duplicates resources (e.g., dynamic memory), while move semantics steals them. Moves are typically O(1) for resource handles, whereas copies are O(n).
Use a simple class like a dynamic array or string to show how copy constructor and copy assignment duplicate data, while move constructor and move assignment transfer ownership.
Mention that move semantics is automatically used for rvalues (temporaries) and when explicitly using std::move. Copy semantics is used for lvalues or when no move is available.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.