Array Deletion at Beginning in DSA Rust - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

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

DSA Rust

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

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

Apush(0)

Bremove(0)

Cclear()

Dpop()

Attempts:

3 left

💡 Hint

Common Mistakes

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

Using clear() removes all elements.

Using push() adds an element instead of removing.

The remove(0) method deletes the element at index 0, which is the first element.

2fill in blank

medium

Complete the code to shift all elements left by removing the first element.

DSA Rust

let mut letters = vec!['a', 'b', 'c', 'd'];
letters.[1](0);
println!("{:?}", letters);

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

Aremove

Bpop

Cclear

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop(0) causes an error because pop() takes no arguments.

Using clear() removes all elements.

Using push() adds elements instead of removing.

The remove(0) method removes the first element and shifts the rest left.

3fill in blank

hard

Fix the error in the code to correctly remove the first element.

DSA Rust

let mut nums = vec![10, 20, 30];
nums.[1](0);
println!("{:?}", nums);

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

Aremove

Bclear

Cpop

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop(0) causes a compile error.

Using clear() removes all elements.

Using push() adds elements instead of removing.

Only remove(0) correctly removes the first element by index.

4fill in blank

hard

Fill both blanks to remove the first element and print the updated vector.

DSA Rust

let mut data = vec![5, 6, 7, 8];
data.[1]([2]);
println!("{:?}", data);

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

Aremove

Bpop

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop with an argument causes an error.

Using index 1 removes the second element, not the first.

Use remove(0) to delete the first element at index 0.

5fill in blank

hard

Fill all three blanks to remove the first element, then add 9 at the end, and print the vector.

DSA Rust

let mut vals = vec![2, 4, 6, 8];
vals.[1]([2]);
vals.[3](9);
println!("{:?}", vals);

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

Aremove

B0

Cpush

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop instead of remove to delete the first element.

Using pop instead of push to add an element.

Using wrong index to remove.

First remove the element at index 0, then push 9 to the end.

Practice

1. What happens when you delete the first element from an array in Rust using remove(0)?

easy

A. The array elements remain unchanged.

B. The last element is removed instead of the first.

C. The array becomes empty regardless of its original size.

D. The first element is removed and all other elements shift left by one position.

Solution

1. Step 1: Understand remove(0) method

   The remove(0) method removes the element at index 0, which is the first element in the array.

2. Step 2: Effect on array elements

   After removal, all elements to the right shift left by one to fill the gap, reducing the array length by one.

3. Final Answer:

   The first element is removed and all other elements shift left by one position. -> Option D

4. Quick Check:

   Deleting at start shifts elements left [OK]

Hint: Deleting at index 0 shifts all elements left by one [OK]

Common Mistakes:

• Thinking last element is removed instead of first
• Assuming array size stays the same
• Believing elements do not shift after deletion

2. Which of the following Rust code snippets correctly deletes the first element from a vector v?

easy

A. v.remove(0);

B. v.delete(0);

C. v.pop_front();

D. v.shift();

Solution

1. Step 1: Identify correct Rust method for deletion at index

   Rust vectors use remove(index) to delete element at a specific position.

2. Step 2: Check other options for validity

   delete, pop_front, and shift are not valid Rust vector methods.

3. Final Answer:

   v.remove(0); -> Option A

4. Quick Check:

   Use remove(0) to delete first element [OK]

Hint: Use remove(0) to delete first element in Rust vector [OK]

Common Mistakes:

• Using non-existent methods like pop_front or shift
• Confusing Rust with other languages' syntax
• Trying to use delete which is invalid in Rust

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

let mut v = vec![10, 20, 30, 40];
v.remove(0);
println!("{:?}", v);

medium

A. [20, 30, 40]

B. [10, 20, 30, 40]

C. [30, 40]

D. [40]

Solution

1. Step 1: Initial vector elements

   The vector v starts as [10, 20, 30, 40].

2. Step 2: Remove first element

   v.remove(0) removes 10, shifting remaining elements left.

3. Step 3: Resulting vector

   After removal, v becomes [20, 30, 40].

4. Final Answer:

   [20, 30, 40] -> Option A

5. Quick Check:

   Remove first element shifts left [OK]

Hint: Removing index 0 drops first element, shifts others left [OK]

Common Mistakes:

• Expecting original vector unchanged
• Thinking multiple elements removed
• Confusing output format

4. Identify the error in this Rust code that tries to delete the first element of a vector:

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

medium

A. Cannot remove elements from a vector.

B. Missing index argument in remove method.

C. remove method does not exist for vectors.

D. Vector cannot be mutable.

Solution

1. Step 1: Check method signature

   The remove method requires an index argument specifying which element to remove.

2. Step 2: Identify missing argument

   The code calls v.remove() without any index, causing a compile error.

3. Final Answer:

   Missing index argument in remove method. -> Option B

4. Quick Check:

   remove needs index argument [OK]

Hint: Always provide index to remove method [OK]

Common Mistakes:

• Calling remove without index
• Thinking remove works like pop() without arguments
• Assuming vector immutability causes error

5. Given a vector v = vec![5, 10, 15, 20, 25], write Rust code to delete the first two elements and print the resulting vector. What will be the output?

hard

A. [5, 10, 15]

B. [10, 15, 20, 25]

C. [15, 20, 25]

D. [20, 25]

Solution

1. Step 1: Remove first element twice

   Calling v.remove(0) twice removes elements at index 0 each time, first 5 then 10.

2. Step 2: Resulting vector after removals

   After removals, vector becomes [15, 20, 25].

3. Final Answer:

   [15, 20, 25] -> Option C

4. Quick Check:

   Two removals at index 0 drop first two elements [OK]

Hint: Remove index 0 repeatedly to delete from start [OK]

Common Mistakes:

• Removing only once instead of twice
• Removing wrong indices after first removal
• Expecting original vector unchanged