Rust Interview Questions and Answers for 7 years experience

1. What is the difference between `Box` and `Rc`?

   • Answer: `Box` represents heap allocation with *single* ownership, ensuring memory safety through Rust's ownership system. `Rc` (Reference Counted) allows *multiple* owners of the same data, enabling shared ownership but requiring careful management to avoid dangling pointers when the last reference is dropped. `Rc` is generally less efficient than `Box` due to the overhead of reference counting.

2. Explain the concept of borrowing in Rust.

   • Answer: Borrowing in Rust is a core mechanism of the ownership system. It allows temporary access to data without transferring ownership. There are mutable and immutable borrows. Mutable borrows allow modification, but only one can exist at a time. Immutable borrows allow reading, and multiple can exist concurrently. This prevents data races.

3. What are lifetimes and why are they important?

   • Answer: Lifetimes are annotations in Rust that specify the scope of a reference. They are crucial for preventing dangling pointers (references to memory that has been freed). The compiler uses lifetimes to ensure that references are always valid, preventing memory safety issues at compile time.

4. Describe the different ways to handle errors in Rust.

   • Answer: Rust primarily uses the `Result` enum to handle errors. `Ok(T)` represents success, and `Err(E)` represents failure. Error handling is explicit; functions returning `Result` must be handled with `match`, `if let`, or the `?` operator (which propagates errors upwards).

5. What is the purpose of the `unsafe` keyword?

   • Answer: The `unsafe` keyword allows bypassing Rust's memory safety and ownership rules. It's used for low-level programming, interacting with C code, or other situations where fine-grained control over memory is needed. However, it must be used cautiously, as incorrect usage can lead to undefined behavior and memory vulnerabilities.

6. Explain the concept of traits in Rust.

   • Answer: Traits define shared behavior for different types. They are similar to interfaces in other languages. Types can implement traits to provide concrete implementations of trait methods. Traits enable polymorphism and code reusability.

7. How do you use generics in Rust?

   • Answer: Generics allow writing code that works with multiple types without knowing the specific type at compile time. They are defined using type parameters within angle brackets (`<>`). This promotes code reusability and avoids code duplication.

8. What are iterators in Rust?

   • Answer: Iterators provide a way to traverse collections (like vectors or sets) lazily. They implement the `Iterator` trait, which provides the `next()` method to get the next element. This allows for efficient processing of large datasets without loading everything into memory at once.

9. Explain the difference between `&str` and `String` in Rust.

   • Answer: `&str` is a string slice, a reference to a string stored elsewhere (often in the data segment or the heap). `String` is a heap-allocated, growable string. `&str` is immutable, while `String` is mutable.

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