Rust hashset

Introduction to Rust hashset

A collection that is used to hold a unique value inside it while not allowing the duplicate values inside the collection is called a HashSet on Rust. It is different from the HashMap in such a way that it does not hold any key-value pairs inside the collection, and the elements inside the collection must be accessed directly. HashSet’s structure is defined inside std::collections of the Rust, which is to be imported in the program at the beginning to be able to make use of HashSet structure, and we make use of the static method new() to create a HashSet.

The syntax to create HashSet in Rust is as follows:

let mut HashSet_name= HashSet::new();
where mut is a keyword to define mutable variable,
HashSet_name is the variable representing the name of the HashSet and
new() is the static method used to create a HashSet

Working of HashSet in Rust

• HashSet is a collection that is used to hold unique values while not allowing duplicate values in Rust.
• The values inside the HashSet must be accessed directly, and HashSet does not hold any key-value pairs.
• The structure of HashSet is defined inside std::collections of the Rust, which is to be imported in the program at the beginning in order to be able to make use of the HashSet structure in the program.
• We make use of the static method new() to create a HashSet.
• The implementation of the HashSet can be done using several functions available in the Rust library.
• The functions available in the Rust library are insert() function, len() function, get() function, iter() function, contains() function, remove() function.
• The insert() function is used to insert the data into the HashSet.
• The len() function is used to obtain the length of the HashSet or the number of elements present in the HashSet.
• The get() function returns a reference to the value if there is a matching value to this value in the HashSet.
• The iter() function is used to access all the elements of the HashSet in a random order of our choice.
• The contains() function returns a value if the value is present in the HashSet.
• The remove() function is used to remove an element from the HashSet,

Examples of Rust hashset

Here are the following example mention below:

Example #1

Rust program to generate to create a HashSet and insert the elements into the HashSet and display the elements present in the HashSet as the output of the program:

//importing std::collections to be able to make use of HashSet in the program
use std::collections::HashSet;
fn main()
{
//defining a mutable variable called country to store the created HashSet
let mut country = HashSet::new();
//using insert() function to insert the elements in the HashSet
country.insert("India");
country.insert("USA");
country.insert("Germany");
//displaying the elements of the HashSet as the output on the screen
println!("The elements present in the HashSet are:");
println!("{:?}", country);
}

The output of the above program is as shown in the snapshot below:

In the above program, we are importing the collections std::collections to be able to make use of HashSet in the program. Then we are creating a new HashSet and defining a mutable variable called the country to store the created HashSet. Then we are using the insert() function to insert the elements in the HashSet. Then the elements of the HashSet is displayed as the output on the screen.

Example #2

Rust program to create a HashSet and demonstrate insert() function, len() function, get() function, remove() function and contains the () function to insert the data into HashSet, determine the length of the HashSet, to determine if an element is present in the HashSet or not and then remove an element and confirm if it is removed or not and then display the result as the output on the screen:

//importing std::collections to be able to make use of HashSet in the program
use std::collections::HashSet;
fn main()
{
//defining a mutable variable called country to store the created HashSet
let mut country = HashSet::new();
//using insert() function to insert the elements in the HashSet
country.insert("India");
country.insert("USA");
country.insert("Germany");
//displaying the elements of the HashSet using iter() function as the output on the screen
println!("The elements present in the HashSet are:");
for coun in country.iter(){
println!("{}", coun);
}
//displaying the length of the HashSet
println!("The length of the HashSet is: {}", country.len());
//using get function to determine if a given element is present in the HashSet or not
match country.get(& "India") {
Some(value) =>  {
println!("The country {} is present in the HashSet", value);
}
None => {
println!("The country is not present in the HashSet");
}
}
//using remove() function to remove an element from the HashSet and checking if the    element is removed or not using contains() function
country.remove( & "USA");
if country.contains( & "USA") {
println!("The country USA is not removed from the HashSet");
}
else {
println!("The country USA is removed from the HashSet");
}
}

The output of the above program is as shown in the snapshot below:

In the above program, we are importing the collections std::collections to be able to make use of HashSet in the program. Then we are creating a new HashSet and defining a mutable variable called the country to store the created HashSet. Then we are using the insert() function to insert the elements in the HashSet. Then, the HashSet elements are displayed as the output on the screen using the iter() function. Then we are making use of the len() function to display the length of the HashSet as the output on the screen. Then we are making use of get() function to determine if an element is present in the HashSet or not. Then we are using the remove() function to remove an element from the HashSet, and then we are using the contains the () function to confirm if the element is removed using the remove() function or not.

Conclusion

In this article, we have learned the concept of HashSet in Rust through definition, syntax, and working of HashSet in Rust with corresponding programming examples and their outputs to demonstrate them.

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