Adding elements to vectors in Rust - Mini Project: Build & Apply

Adding elements to vectors

📖 Scenario: You are managing a list of fruits you want to buy from the market. You will start with an empty list and add fruits one by one.

🎯 Goal: Build a Rust program that creates an empty vector of strings, adds fruit names to it, and then prints the final list.

📋 What You'll Learn

Create an empty vector called fruits to hold String values

Add the fruit "Apple" to the fruits vector

Add the fruit "Banana" to the fruits vector

Add the fruit "Cherry" to the fruits vector

Print the fruits vector to show all fruits added

💡 Why This Matters

🌍 Real World

Vectors are used to store lists of items like shopping lists, user inputs, or data records in many programs.

💼 Career

Understanding how to add elements to vectors is essential for managing collections of data efficiently in Rust programming jobs.

1

Create an empty vector

Create an empty vector called fruits that can hold String values.

Rust

# Your code here

Hint

Use Vec::new() to create an empty vector and make it mutable with mut.

2

Add the first fruit

Add the fruit "Apple" to the fruits vector using the push method.

Rust

let mut fruits: Vec = Vec::new();
# Your code here

Hint

Use fruits.push(String::from("Apple")) to add "Apple" to the vector.

3

Add more fruits

Add the fruits "Banana" and "Cherry" to the fruits vector using the push method twice.

Rust

let mut fruits: Vec = Vec::new();
fruits.push(String::from("Apple"));
# Your code here

Hint

Use fruits.push(String::from("Banana")) and fruits.push(String::from("Cherry")) to add the fruits.

4

Print the fruits vector

Print the fruits vector using println! to show all fruits added.

Rust

let mut fruits: Vec = Vec::new();
fruits.push(String::from("Apple"));
fruits.push(String::from("Banana"));
fruits.push(String::from("Cherry"));
# Your code here

Hint

Use println!("{:?}", fruits); to print the vector in debug format.

Practice

1. What does the push method do when used on a Rust vector?

easy

A. Removes the last element from the vector

B. Adds a new element to the end of the vector

C. Creates a new vector with one element

D. Sorts the elements in the vector

Solution

1. Step 1: Understand the purpose of push

   The push method is used to add elements to a vector in Rust.

2. Step 2: Identify what push does specifically

   It adds a new element to the end of the vector, increasing its size by one.

3. Final Answer:

   Adds a new element to the end of the vector -> Option B

4. Quick Check:

   push adds element [OK]

Hint: Remember: push always adds at the end [OK]

Common Mistakes:

• Confusing push with pop (which removes elements)
• Thinking push creates a new vector
• Assuming push sorts the vector

2. Which of the following is the correct way to declare a mutable vector and add the number 10 to it in Rust?

easy

A. let v = Vec::new(); v.add(10);

B. let v = Vec::new(); v.push(10);

C. let mut v = Vec::new(); v.add(10);

D. let mut v = Vec::new(); v.push(10);

Solution

1. Step 1: Check vector mutability

   To add elements, the vector must be mutable, so let mut v is required.

2. Step 2: Use correct method to add element

   The method to add an element is push, not add.

3. Final Answer:

   let mut v = Vec::new(); v.push(10); -> Option D

4. Quick Check:

   Mutable vector + push method [OK]

Hint: Mutable vector + push method adds elements [OK]

Common Mistakes:

• Forgetting to make the vector mutable
• Using a non-existent method like add
• Trying to push on an immutable vector

3. What will be the output of this Rust code?

let mut v = vec![1, 2];
v.push(3);
println!("{:?}", v);

medium

A. [1, 2]

B. Compilation error

C. [1, 2, 3]

D. [3, 1, 2]

Solution

1. Step 1: Understand initial vector content

   The vector starts with elements [1, 2].

2. Step 2: Apply the push method

   The push(3) adds 3 at the end, so vector becomes [1, 2, 3].

3. Final Answer:

   [1, 2, 3] -> Option C

4. Quick Check:

   push adds element at end [OK]

Hint: push adds element at the end of vector [OK]

Common Mistakes:

• Expecting push to add at the start
• Thinking push replaces elements
• Assuming code causes error

4. Identify the error in this Rust code snippet:

let v = Vec::new();
v.push(5);

medium

A. Vector is not mutable, so push cannot be called

B. push method does not exist for vectors

C. Vec::new() cannot create an empty vector

D. Missing semicolon after Vec::new()

Solution

1. Step 1: Check vector mutability

   The vector is declared as immutable with let v, so it cannot be changed.

2. Step 2: Understand push method requirements

   The push method requires the vector to be mutable to add elements.

3. Final Answer:

   Vector is not mutable, so push cannot be called -> Option A

4. Quick Check:

   push needs mutable vector [OK]

Hint: Make vector mutable to use push [OK]

Common Mistakes:

• Assuming push works on immutable vectors
• Thinking Vec::new() is invalid
• Ignoring mut keyword necessity

5. You want to add multiple elements [4, 5, 6] to an existing mutable vector v. Which code correctly adds all these elements efficiently?

hard

A. v.extend([4, 5, 6]);

B. v.push(4, 5, 6);

C. v.add([4, 5, 6]);

D. v.push([4, 5, 6]);

Solution

1. Step 1: Understand adding multiple elements

   Using push adds one element at a time, so multiple calls are needed for multiple elements.

2. Step 2: Use the efficient method for multiple elements

   The extend method adds all elements from an iterable at once, which is more efficient.

3. Final Answer:

   v.extend([4, 5, 6]); -> Option A

4. Quick Check:

   Use extend for multiple elements [OK]

Hint: Use extend to add many elements at once [OK]

Common Mistakes:

• Using push with a whole array (causes error)
• Using non-existent add method
• Calling push multiple times instead of extend