LinkedIn skill assessment answers and questions — Rust (Язык программирования)

“Ржавчина is a modern and innovative programming language that has gained popularity for its focus on performance, безопасность, and concurrency. В этом подробном руководстве, we’re thrilled to present a series of вопросы для оценки навыков а также ответы specifically tailored for Ржавчина пользователи.

Whether you’re a seasoned developer looking to expand your capabilities or a beginner aiming to understand the basics of this powerful language, this resource is designed to help you become proficient in Ржавчина and its applications. Join us as we explore the core concepts of Rust programming, including ownership, borrowing, lifetimes, и более, empowering you to harness the full potential of this cutting-edge language.”

Q1. Which type cast preserves the mathematical value in all cases?

i64 as i32
usize as u64
i32 as i64
f64 as f32

2 квартал. What do the vertical bars represent here?

str::thread::spawn(|| {
    println!("LinkedIn");
});

a closure
a thread
a future
a block

ссылка

3 квартал. Which choice is not a scalar data type?

integer
плавать
boolean
tuple

4 квартал. _ cannot be destructured.

Traits
Кортежи
Enums
Structs

ссылка

Q5. Который `cargo` command checks a program for error without creating a binary executable?

cargo –версия
cargo init
cargo build
cargo check

Q6. Период, термин коробка and related phrases such as boxing a value are often used when relating to memory layout. What does коробка refer to?

It’s creating a pointer on the heap that points to a value on the stack.
It’s creating a pointer on the stack that points to a value on the heap.
It’s creating a memory guard around values to prevent illegal access.
It’s an abstraction that refers to ownership. “Boxed” values are clearly labelled.

Q7. What is an alternative way of writing `slice` that produces the same result?

...
let s = String::form("hello");
let slice = &s[0..2];

let slice = &s[len + 2];
let slice = &s[len – 2];
let slice = &s.copy(0..2);
let slice = &s[..2];

Q8. С использованием `?` operator at the end of an expression is equivalent to _.

a match pattern that branches into True or False
calling ok_error()
calling panic!()
a match pattern that may result an early return

Q9. Which is valid syntax for defining an array of i32 values?

Множество::with_capacity(10)
[i32]
Множество::новый(10)
[i32; 10]

Q10. What syntax is required to take a mutable reference to T, when used within a function argument?

fn increment(i: T) {
    // body elided
}

*mut T
mut ref T
mut &T
&mut T

Вам нужно будет достичь как минимум. The smart pointers Rc and Arc provide reference counting. What is the API for incrementing a reference count?

.добавлять()
.incr()
.clone()
.increment()

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Q12. What happens when an error occurs that is being handled by the question mark (?) operator?

The error is reported and execution continues.
An exception is raised. The effect(s) of the exception are defined by the error! macro.
The program panics immediately.
Rust attempts to convert the error to the local function’s error type and return it as Result::Err. If that fails, the program panics.

Q13. Which comment syntax is not legal?

/*
#
//!
//

Q14. In matching patterns, values are ignored with _.

.ignore()
an underscore (_)
..
пропускать

Q15. Defining a _ requires a lifetime parameter.

function that ends the lifetime of one of its arguments
struct that contains a reference to a value
function with a generic argument
struct that contains a reference to a boxed value

Rust book reference

Q16. Which example correctly uses std::коллекции::HashMap’s Entry API to populate counts?

use std::collections::HashMap;
fn main() {
    let mut counts = HashMap::new();
    let text = "LinkedIn Learning";
    for c in text.chars() {
        // Complete this block
    }
    println!("{:?}", counts);
}

for c in text.chars() {
    if let Some(count) = &mut counts.get(&c) {
        counts.insert(c, *count + 1);
    } else {
        counts.insert(c, 1);
    };
}

for c in text.chars() {
    let count = counts.entry(c).or_insert(0);
    *count += 1;
}

for c in text.chars() {
    let count = counts.entry(c);
    *count += 1;
}

for c in text.chars() {
    counts.entry(c).or_insert(0).map(|x| x + 1);
}

ссылка

Q17. Which fragment does not incur memory allocations while writing to a “файл” (represented by a Vec)?

use std::collections::HashMap;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut v = Vec::<u8>::new();

    let a = "LinkedIn";
    let b = 123;
    let c = '🧀';

    // replace this line

    println!("{:?}", v);

    Ok(())
}

write!(&mut v, "{}{}{}", a, b, c)?;

v.write(a)?;
v.write(b)?;
v.write(c)?;

v.write(a, b, c)?;

v.write_all(a.as_bytes())?;
v.write_all(&b.to_string().as_bytes())?;
c.encode_utf8(&mut v);

Q18. Does the `main` function compile? Если так, Почему? Если не, what do you need to change?

fn main() {
    let Some(x) = some_option_value;
}

The code does not compile. let statements require a refutable pattern. Добавлять if до let.
The code compiles. let statements sometimes require a refutable pattern.
The code does not compile. let statements requires an irrefutable pattern. Добавлять if до let.
The code compiles. let do not require a refutable pattern.

Q19. Which statement about lifetimes is false?

Lifetimes were redundantly specified in previous version of Rust.
Lifetimes are specified when a struct is holding a reference to a value.
Lifetimes are specified when certain values must outlive others.
Lifetimes are always inferred by the compiler.

Q20. When used as a return type, which Rust type plays a similar role to Python’s `None`, JavaScript’s `null`, or the `void` type in C/C++?

!
None
Null
()

Q21. To convert a `Result` to an `Option`, which method should you use?

.as_option()
.ok()
.to_option()
.into()

Q22. Which statement about the `Clone` а также `Copy` traits is false?

Copy is enabled for primitive, built-in types.
Without Copy, Rust applies move semantics to a type’s access.
When using Clone, copying data is explicit.
Until a type implements either Copy или же Clone, its internal data cannot be copied.

ref from stack overflow

Q23. Why does this code не compile?

fn returns_closure() -> dyn Fn(i32) -> i32 {
    |x| x + 1
}

The returned fn pointer and value need to be represented by another trait.
Closures are types, so they cannot be returned directly from a function.
Closures are types and can be returned only if the concrete trait is implemented.
Closures are represented by traits, so they cannot be a return type.

Rust book reference

Q24. What smart pointer is used to allow multiple ownership of a value in various threads?

Arc<T>
Box<T>
Both Arc<T> а также Rc<T> are multithread safe.
Rc<T>

Rust book reference

Q25. Which types are не allowed within an enum variant’s body?

zero-sized types
структуры
trait objects
floating-point numbers

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LinkedIn skill assessment answers and questions — Rust (Язык программирования)