Common Collections

Question 1

What do vectors allow for?

Answer 1

Storing more than one value in a single data structure that puts all the values next to each other in memory.

Question 2

What is the syntax to create a new empty vector?

Answer 2

let v: Vec = Vec::new();

Question 3

What does let v = vec![1, 2, 3]; do

Answer 3

Uses the vec macro to create a new Vec that holds the values 1, 2, and 3, and assign it to the variable v.

Question 4

What is the method used to add values to a vector?

Answer 4

push()

Question 5

What are the two ways to read values from a vector?

Answer 5

By using & and [], which gives a reference, or by using the get method with the index passed as an argument, which gives an Option.

Question 6

How can you iterate over a vector v?

Answer 6

for i in &mut v {
    // Do something.
}

Question 7

How can we store multiple types in a vector?

Answer 7

Create an enum with whatever types needed, and a vector that stores the enum type.

Question 8

How are strings implemented in Rust?

Answer 8

As a collection of bytes, plus some methods to provide useful functionality when those bytes are interpreted as text.

Question 9

What is the one string type in the Rust core language?

Answer 9

The string slice str that is usually seen in its borrowed form &str

Question 10

Where is Rusts String type provided?

Answer 10

The standard library.

Question 11

What is the encoding for both String and string slices?

Answer 11

UTF-8

Question 12

What is the syntax to create a new String in Rust?

Answer 12

let mut s = String::new();

Question 13

What does the to_string() do on a string literal?

Answer 13

Creates a String from a string literal.
let s = "initial contents".to_string();

Question 14

What does the String::from function do?

Answer 14

Creates a String for a string literal.
let s = String::from("initial contents");

Question 15

What is the method to push to a string slice?

Answer 15

push_str().

Question 16

What does the push method do to a String?

Answer 16

Takes a single character as a param and adds it to the string.

Question 17

What are two ways to concatenate strings in Rust?

Answer 17

+ and format!

Question 18

What is a String in Rust?

Answer 18

A wrapper over a Vec.

Question 19

Why is referencing into a String by index not allowed in Rust?

Answer 19

Because it would return the byte value corresponding to the index which might not equate to a correct unicode scalar value. Also because indexing operations are supposed to take O(1) and Rust cannot guarantee that.

Question 20

What does the chars() do when used with a string?

Answer 20

Iterates over the string returning each Unicode scalar value.

Question 21

What does the bytes() do when used with a string

Answer 21

Iterates over the string and returns each byte.

Question 22

What is the use statement for HashMap?

Answer 22

use std::collections::HashMap;

Question 23

What is the syntax to create a new HashMap?

Answer 23

let mut scores = HashMap::new();