Adding elements to vectors in Rust - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add the number 5 to the vector.

Rust

let mut numbers = vec![1, 2, 3];
numbers.[1](5);

Drag options to blanks, or click blank then click option'

Apush

Bpop

Cinsert

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop removes an element instead of adding.

Using insert requires an index.

The push method adds an element to the end of the vector.

2fill in blank

medium

Complete the code to add the number 10 at the start of the vector.

Rust

let mut numbers = vec![2, 3, 4];
numbers.[1](0, 10);

Drag options to blanks, or click blank then click option'

Ainsert

Bpush

Cpop

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using push adds to the end, not the start.

Using pop or remove removes elements.

The insert method adds an element at a specific index in the vector.

3fill in blank

hard

Fix the error in the code to add 7 to the vector.

Rust

let mut nums = vec![1, 2, 3];
nums.[1](7);

Drag options to blanks, or click blank then click option'

Aappend

Binsert

Cextend

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using append or extend requires another vector or iterable.

Using insert needs an index.

The push method correctly adds a single element to the vector.

4fill in blank

hard

Fill both blanks to add 20 at index 1 and then add 30 at the end.

Rust

let mut vals = vec![10, 15];
vals.[1](1, 20);
vals.[2](30);

Drag options to blanks, or click blank then click option'

Ainsert

Bpush

Cremove

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove or pop removes elements instead of adding.

insert adds an element at a specific index, and push adds at the end.

5fill in blank

hard

Fill all three blanks to add 100 at index 0, then add 200 and 300 at the end.

Rust

let mut data = vec![400];
data.[1](0, 100);
data.[2](200);
data.[3](300);

Drag options to blanks, or click blank then click option'

Ainsert

Bpush

Cappend

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using append to add single elements causes errors.

Using pop removes elements.

insert adds at a specific index, and push adds elements at the end. append is for adding another vector, not single elements.

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