Why input and output are required in Rust - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to read a number from the user and print it.

Rust

fn main() {
    let mut input = String::new();
    std::io::stdin().read_line(&mut [1]).expect("Failed to read line");
    println!("You entered: {}", input.trim());
}

Drag options to blanks, or click blank then click option'

Ainput

Boutput

Cbuffer

Dline

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a variable that is not mutable or not declared.

The variable input is used to store the user input. We must pass it to read_line to fill it with the input data.

2fill in blank

medium

Complete the code to convert the input string to an integer.

Rust

fn main() {
    let mut input = String::new();
    std::io::stdin().read_line(&mut input).expect("Failed to read line");
    let number: i32 = [1].trim().parse().expect("Please type a number!");
    println!("Number is: {}", number);
}

Drag options to blanks, or click blank then click option'

Anumber

Bline

Cinput

Dbuffer

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to parse a variable that is not a string.

The variable input holds the string read from the user. We trim and parse it to convert to an integer.

3fill in blank

hard

Fix the error in the code to print the sum of two numbers read from input.

Rust

fn main() {
    let mut input1 = String::new();
    let mut input2 = String::new();
    std::io::stdin().read_line(&mut input1).expect("Failed to read line");
    std::io::stdin().read_line(&mut input2).expect("Failed to read line");
    let num1: i32 = input1.trim().parse().expect("Not a number");
    let num2: i32 = input2.trim().parse().expect("Not a number");
    let sum = num1 + [1];
    println!("Sum is: {}", sum);
}

Drag options to blanks, or click blank then click option'

Anum2

Bnum1

Cinput1

Dinput2

Attempts:

3 left

💡 Hint

Common Mistakes

Adding the string variables instead of parsed integers.

The sum should add num1 and num2. The blank must be filled with num2.

4fill in blank

hard

Fill both blanks to create a dictionary with word lengths for words longer than 3 letters.

Rust

fn main() {
    let words = vec!["apple", "cat", "banana", "dog"];
    let lengths: std::collections::HashMap<_, _> = words.iter()
        .filter(|&&word| word.len() [1] 3)
        .map(|&word| (word, word.[2]()))
        .collect();
    println!("{:?}", lengths);
}

Drag options to blanks, or click blank then click option'

A>

B<

Clen

Dto_string

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong comparison operator or wrong method to get length.

We filter words with length greater than 3 using word.len() > 3. Then map each word to its length using word.len().

5fill in blank

hard

Fill all three blanks to create a dictionary with uppercase keys and values for words longer than 4 letters.

Rust

fn main() {
    let words = vec!["apple", "cat", "banana", "dog"];
    let result: std::collections::HashMap<_, _> = words.iter()
        .filter(|&&word| word.len() [1] 4)
        .map(|&word| (word.[2](), word.[3]()))
        .collect();
    println!("{:?}", result);
}

Drag options to blanks, or click blank then click option'

A>

Bto_string

Cto_uppercase

Dlen

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong methods or wrong comparison operators.

Filter words longer than 4 with word.len() > 4. Map keys to uppercase with word.to_uppercase() and values to strings with word.to_string().