Array Insertion at Beginning in DSA Rust - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to insert a value at the beginning of the vector.

DSA Rust

let mut numbers = vec![2, 3, 4];
numbers.[1](0, 1);
println!("{:?}", numbers);

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

Apush

Binsert

Cappend

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using push adds to the end, not the beginning.

Using remove deletes elements instead of adding.

The insert method allows adding an element at a specific index. Using insert(0, value) adds the value at the beginning.

2fill in blank

medium

Complete the code to insert the value 10 at the start of the vector.

DSA Rust

let mut data = vec![20, 30, 40];
data.[1](0, 10);
println!("{:?}", data);

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

Aextend

Bremove

Cinsert

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using push instead of insert.

Using extend which adds multiple elements.

Using insert(0, 10) adds 10 at the beginning of the vector.

3fill in blank

hard

Fix the error in the code to insert 5 at the beginning of the vector.

DSA Rust

let mut nums = vec![6, 7, 8];
nums.[1](0, 5);
println!("{:?}", nums);

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

Aremove

Bpush

Cappend

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove deletes elements instead of adding.

Using push adds at the end, not the beginning.

The insert method requires an index and a value. To insert at the beginning, use insert(0, 5).

4fill in blank

hard

Fill both blanks to insert 100 at the start of the vector and print it.

DSA Rust

let mut vals = vec![200, 300, 400];
vals.[1]([2], 100);
println!("{:?}", vals);

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

Ainsert

Bpush

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using push instead of insert.

Using index 1 instead of 0 to insert at the start.

Use insert with index 0 to add 100 at the beginning.

5fill in blank

hard

Fill all three blanks to insert 0 at the beginning, then print the vector length.

DSA Rust

let mut arr = vec![1, 2, 3];
arr.[1]([2], 0);
println!("Length: {}", arr.[3]());

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

Ainsert

Blen

C0

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using push instead of insert for adding at start.

Using wrong index instead of 0.

Using incorrect method to get length.

Use insert(0, 0) to add 0 at the start. Then use len() to get the vector length.

Practice

1. What happens when you insert an element at the beginning of a vector in Rust using insert(0, value)?

easy

A. The element is added at the end of the vector.

B. The element is added at the start, and all other elements shift right by one position.

C. The element replaces the first element without shifting others.

D. The vector size remains the same and no element is added.

Solution

1. Step 1: Understand insert(0, value) behavior

   In Rust, calling insert(0, value) on a vector adds the value at index 0.

2. Step 2: Effect on existing elements

   All existing elements shift one position to the right to make space for the new element.

3. Final Answer:

   The element is added at the start, and all other elements shift right by one position. -> Option B

4. Quick Check:

   Insert at index 0 shifts elements right [OK]

Hint: Insert at index 0 shifts all elements right [OK]

Common Mistakes:

• Thinking insert replaces the first element
• Assuming insert adds at the end
• Believing array size stays the same

2. Which of the following Rust code snippets correctly inserts the value 10 at the beginning of a vector named vec?

easy

A. vec.insert(0, 10);

B. vec.push(10);

C. vec[0] = 10;

D. vec.add(0, 10);

Solution

1. Step 1: Identify correct method for insertion at index

   Rust vectors use insert(index, value) to add elements at a specific position.

2. Step 2: Check each option

   vec.insert(0, 10); uses insert(0, 10), which inserts 10 at the start. vec.push(10); adds at the end. vec[0] = 10; replaces the first element without insertion. vec.add(0, 10); is invalid syntax.

3. Final Answer:

   vec.insert(0, 10); -> Option A

4. Quick Check:

   Use insert(0, value) to add at start [OK]

Hint: Use insert(0, value) to add at beginning [OK]

Common Mistakes:

• Using push() adds at end, not beginning
• Assigning vec[0] replaces element, no insertion
• Using non-existent method add()

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

let mut vec = vec![2, 3, 4];
vec.insert(0, 1);
println!("{:?}", vec);

medium

A. [2, 3, 4, 1]

B. [2, 3, 4]

C. [1, 3, 4]

D. [1, 2, 3, 4]

Solution

1. Step 1: Initial vector state

   The vector starts as [2, 3, 4].

2. Step 2: Insert 1 at index 0

   Using vec.insert(0, 1) adds 1 at the start, shifting others right.

3. Final Answer:

   [1, 2, 3, 4] -> Option D

4. Quick Check:

   Insert at start shifts elements right [OK]

Hint: Insert at 0 adds element at front, shifts others right [OK]

Common Mistakes:

• Expecting element added at end
• Thinking insert replaces element
• Ignoring vector shift after insert

4. Identify the error in this Rust code:

let mut vec = vec![1, 2, 3];
vec.insert(5, 0);

medium

A. The index 5 is out of bounds for the vector of length 3.

B. The vector is immutable; it should be declared mutable.

C. The insert method parameters are reversed; index should be first, value second.

D. The insert method does not exist for vectors.

Solution

1. Step 1: Analyze the insert index

   The vector has length 3, valid insert indices are 0 to 3. Index 5 is out of bounds, causing runtime panic.

2. Step 2: Confirm syntax and mutability

   Parameters follow correct order insert(index, value); vector is declared mutable.

3. Final Answer:

   The index 5 is out of bounds for the vector of length 3. -> Option A

4. Quick Check:

   Insert index must be within vector bounds [OK]

Hint: Check insert(index, value) and index within vector length [OK]

Common Mistakes:

• Reversing insert parameters
• Using out-of-range index
• Forgetting to declare vector mutable

5. You have a vector vec = vec![10, 20, 30]. You want to insert multiple values [1, 2, 3] at the beginning efficiently. Which approach is best in Rust?

hard

A. Use a loop to insert each element at index 0 one by one.

B. Replace the original vector with the new elements only.

C. Create a new vector with the new elements, then extend it with the original vector.

D. Use vec.push() for each new element and then reverse the vector.

Solution

1. Step 1: Analyze inserting multiple elements at start

   Inserting one by one at index 0 shifts elements repeatedly, inefficient for multiple inserts.

2. Step 2: Efficient approach

   Create a new vector with new elements, then extend it with the original vector to combine efficiently.

3. Final Answer:

   Create a new vector with the new elements, then extend it with the original vector. -> Option C

4. Quick Check:

   Prepending by new vector + extend is efficient [OK]

Hint: Prepend multiple by new vector + extend original [OK]

Common Mistakes:

• Inserting elements one by one at index 0 (slow)
• Using push then reversing (extra steps)
• Replacing original vector loses data