Rust Programming Master Class from Beginner to Expert - Hash Maps

This tutorial covers the concept of hash maps, their analogy to dictionaries, and their implementation in Rust. It explains how to create, add, access, and update values in a hash map. The tutorial also demonstrates checking for key existence and iterating over hash map entries. An example of using hash maps for frequency counting is provided, illustrating practical applications. The tutorial concludes with a discussion on the use of hash maps in advanced topics.

What is a key characteristic of keys in a hash map?

• Keys can be duplicated.

• Keys must be integers.

• Keys are unique with no duplicates allowed.

• Keys must be strings.

In Rust, how do you declare a new empty hash map?

• let person = new HashMap();

• let person = HashMap::create();

• let mut person = HashMap::initialize();

• let mut person = HashMap::new();

Which function is used to access a value in a hash map by its key?

• search()

• locate()

• get()

• find()

What does the contains_key function return?

• A float

• An integer

• A string

• A boolean

How can you iterate over all key-value pairs in a hash map?

• Using a while loop

• Using a for loop

• Using a repeat-until loop

• Using a do-while loop

Why might the order of elements change when iterating over a hash map?

• Because hash maps are stored on the heap and not in contiguous locations.

• Because hash maps are sorted by default.

• Because hash maps are stored in contiguous memory locations.

• Because hash maps are stored on the stack.

What happens when you use the insert function on an existing key in a hash map?

• The existing value is updated.

• A new key is created.

• The existing value is deleted.

• Nothing happens.

How does the entry function differ from the insert function?

• It always updates the value.

• It only updates the value if no value exists for the key.

• It deletes the existing value.

• It creates a new key.

In the practical example, what is stored as keys in the hash map?

• The distinct values from the vector

• The indices of the vector

• The average of the vector elements

• The sum of the vector elements

What is the purpose of using a mutable reference in the frequency counting example?

• To delete a key-value pair

• To update the frequency count for each key

• To sort the hash map

• To change the key of the hash map