What is RAII (Resource Acquisition Is Initialization) in C++ and how do smart pointers (unique_ptr, shared_ptr, weak_ptr) prevent memory leaks?

RAII is a core C++ programming idiom where resource lifecycle is tied to object lifetime. Resources (heap memory, file handles, mutex locks) are acquired during constructor initialization and released automatically in the destructor when the object goes out of scope.

Smart Pointers:

• std::unique_ptr: Exclusive ownership model. Cannot be copied, only moved (std::move). Releases memory automatically upon scope termination with zero overhead compared to raw pointers.
• std::shared_ptr: Shared ownership model utilizing an atomic reference-count control block. When the last owner is destroyed, reference count reaches 0 and managed memory is freed.
• std::weak_ptr: Non-owning observer that references a shared_ptr managed object without incrementing reference count. Essential for breaking circular reference deadlocks.