Array Deletion at End in DSA Rust - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove the last element from the vector.

DSA Rust

let mut numbers = vec![1, 2, 3, 4, 5];
numbers.[1]();
println!("{:?}", numbers);

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

Apop

Binsert

Cpush

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using push() instead of pop() adds elements instead of removing.

Using remove() requires an index, not suitable for just last element.

The pop() method removes the last element from the vector.

2fill in blank

medium

Complete the code to safely remove the last element and print it.

DSA Rust

let mut letters = vec!["a", "b", "c"];
if let Some(last) = letters.[1]() {
    println!("Removed: {}", last);
}
println!("{:?}", letters);

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

Aremove

Bpop

Cinsert

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove() without index causes error.

Using push() adds elements instead of removing.

pop() returns an Option with the last element removed, allowing safe handling.

3fill in blank

hard

Fix the error in the code to remove the last element from the vector.

DSA Rust

let mut nums = vec![10, 20, 30];
nums.[1](nums.len() - 1);
println!("{:?}", nums);

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

Aremove

Bpush

Cpop

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop() with an argument causes error.

Using remove() with index equal to length causes panic.

remove() is the method that removes by index. nums.len() - 1 gives the index of the last element.

4fill in blank

hard

Fill both blanks to remove the last element by index safely.

DSA Rust

let mut data = vec![100, 200, 300];
if data.len() > 0 {
    data.[1](data.[2]() - 1);
}
println!("{:?}", data);

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

Aremove

Blen

Cpop

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop() with index causes error.

Using len() without subtracting 1 causes out-of-bounds panic.

remove() deletes element at given index; len() returns vector length, so len() - 1 is last index.

5fill in blank

hard

Fill the blank to remove the last element and print it if exists.

DSA Rust

let mut items = vec!["x", "y", "z"];
if let Some(removed) = items.[1]() {
    println!("Removed: {}", removed);
}
println!("Remaining: {:?}", items);

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

Ainsert

Bremove

Cpop

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove() without index causes error.

Using push() or insert() adds elements instead of removing.

pop() removes and returns the last element safely as an Option.

Practice

1. What happens when you remove the last element from a Rust Vec using pop()?

easy

A. The last element is removed and returned as Some(value).

B. The first element is removed and returned.

C. The entire vector is cleared.

D. The vector becomes immutable.

Solution

1. Step 1: Understand pop() behavior

   The pop() method removes the last element from the vector and returns it wrapped in Some(value) if the vector is not empty.

2. Step 2: Confirm it does not affect other elements

   Only the last element is removed; the rest of the vector remains unchanged.

3. Final Answer:

   The last element is removed and returned as Some(value). -> Option A

4. Quick Check:

   pop() removes last element [OK]

Hint: pop() removes and returns last element wrapped in Some [OK]

Common Mistakes:

• Thinking pop() removes the first element
• Assuming pop() clears the entire vector
• Believing pop() makes vector immutable

2. Which of the following is the correct syntax to remove the last element from a mutable vector v in Rust?

easy

A. v.erase_last();

B. v.remove_last();

C. v.delete_end();

D. v.pop();

Solution

1. Step 1: Recall Rust vector methods

   The standard method to remove the last element from a vector is pop().

2. Step 2: Check method names

   Methods like remove_last(), delete_end(), and erase_last() do not exist in Rust's Vec API.

3. Final Answer:

   v.pop(); -> Option D

4. Quick Check:

   Correct method to remove last element is pop() [OK]

Hint: Use pop() to remove last element from vector [OK]

Common Mistakes:

• Using non-existent methods like remove_last()
• Confusing pop() with remove() which removes by index
• Trying to use erase_last() or delete_end() which are invalid

3. What is the output of the following Rust code?

let mut v = vec![10, 20, 30];
let x = v.pop();
println!("{:?}", v);
println!("{:?}", x);

medium

A. [10, 20]
None

B. [10, 20, 30]
None

C. [10, 20]
Some(30)

D. [20, 30]
Some(10)

Solution

1. Step 1: Understand pop() effect on vector

   The pop() removes the last element, which is 30, and returns Some(30).

2. Step 2: Check vector after pop

   After removal, the vector contains [10, 20].

3. Final Answer:

   [10, 20] Some(30) -> Option C

4. Quick Check:

   pop() removes last element 30, vector left with [10, 20] [OK]

Hint: pop() returns last element and shortens vector [OK]

Common Mistakes:

• Expecting pop() to remove first element
• Assuming pop() returns None when vector is not empty
• Confusing vector contents after pop

4. Identify the error in the following Rust code that tries to remove the last element from a vector:

let v = vec![1, 2, 3];
v.pop();

medium

A. pop() method does not exist for vectors.

B. Cannot call pop() on an immutable vector.

C. pop() removes the first element, not the last.

D. The vector must be empty before calling pop().

Solution

1. Step 1: Check vector mutability

   The vector v is declared immutable with let. To modify it, it must be mutable.

2. Step 2: Understand pop() requirements

   The pop() method requires a mutable vector to remove the last element.

3. Final Answer:

   Cannot call pop() on an immutable vector. -> Option B

4. Quick Check:

   pop() needs mutable vector [OK]

Hint: Make vector mutable with 'mut' before pop() [OK]

Common Mistakes:

• Trying to pop from immutable vector
• Thinking pop() removes first element
• Assuming pop() works on empty vector without error

5. Given a vector v with elements [5, 10, 15, 20], write Rust code to remove the last two elements and print the resulting vector. What will be printed?

hard

A. [5, 10]

B. [5, 10, 15]

C. [15, 20]

D. [5, 10, 15, 20]

Solution

1. Step 1: Remove last element twice using pop()

   Calling pop() twice removes 20 then 15, leaving [5, 10].

2. Step 2: Print the vector after removals

   Printing v now shows [5, 10].

3. Final Answer:

   [5, 10] -> Option A

4. Quick Check:

   Two pops remove last two elements [OK]

Hint: Call pop() twice to remove last two elements [OK]

Common Mistakes:

• Removing only one element instead of two
• Confusing pop() with remove(index)
• Expecting vector to be empty after two pops