Collections

In this exercise, you will learn how to work with Rust standard collections. The documentation of the std::collections is excellent and provides an overview of the most important containers which are also included in the standard library.

You will learn to:

• Read user input from the terminal.
• Use the Rust std::vec::Vec dynamic array container.
• Sort sequences.
• Use the Rust std::collections::BTreeSet sorted set container.
• Use the std::collections::HashMap map container.

You can find the solutions here.

Task

1. Create a new binary crate called collections
2. Read in a string of space separated words from Standard Input and place them into a vector. Then sort the vector and print the sorted list.
3. Repeat step 2, but use the std::collections::BTreeSet container instead which keeps the elements in sorted order. Print the list again.
4. Create a second binary inside the package by creating a bin folder inside the src folder and creating a new map.rs file inside it.
5. Read in a string with the syntax key1:value1,key2:value2 and store the key-value pairs in a std::collections::HashMap. A nice solution also deals with extra whitespace, e.g. key1: value1, key2: value2.

Hints

These hints can help you with completing individual steps.

Reading input from the console

The std::io module contains everything required to read from the console or write to the console. The operating system models those using pre-defined standard streams. The Standard In, Out and Error streams are exposed by the std::io::stdin, std::io::stdout and std::io::stderr functions.

The std::io::Stdin handle implements the std::io::Read trait and also exposes the read_line method to help with this task. This function expects a mutable reference to a String, so you need to create an empty one before calling it.

#![allow(unused)]
fn main() {
    let mut input_string = std::string::String::new();
    std::io::stdin().read_line(&mut input_string).expect("reading input string failed");
}

Word extraction

Rust provides useful APIs for string manipulation and extraction. You might find the following APIs useful:

Sorting a vector

The Vec data structure has a lot of useful methods, including sorters.

Quiz

After you have worked through this exercise, you can try this quiz to double check your understanding:

Q1:

How does the sort method or the BTreeSet know how to order elements? Why did it just magically know how to sort our strings/words?

Hint:

Answer:

Q2:

What is the advantage of using &str over String?

Hint:

Answer: