Linked List vs Array When to Choose Which in DSA Rust - Interactive Comparison Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an empty vector (array) in Rust.

DSA Rust

let mut numbers = Vec::[1]();

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

Aempty

Bnew

Cinit

Dcreate

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like empty(), init(), or create()

In Rust, Vec::new() creates a new empty vector (array).

2fill in blank

medium

Complete the code to add an element to the end of a linked list in Rust.

DSA Rust

linked_list.[1](value);

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

Apush_back

Bpush_front

Cinsert

Dappend

Attempts:

3 left

💡 Hint

Common Mistakes

Using push_front adds at the start, not the end.

To add an element at the end of a linked list, use push_back.

3fill in blank

hard

Fix the error in accessing the third element of a vector safely.

DSA Rust

let third = numbers.[1](2);

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

Aget

Bat

Cindex

Dfetch

Attempts:

3 left

💡 Hint

Common Mistakes

Using index operator or methods that panic on invalid index.

The get method returns an Option safely without panicking if the index is out of bounds.

4fill in blank

hard

Fill both blanks to create a linked list and add an element at the front.

DSA Rust

let mut list = LinkedList::[1]();
list.[2](10);

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

Anew

Bpush_back

Cpush_front

Dcreate

Attempts:

3 left

💡 Hint

Common Mistakes

Using push_back instead of push_front for adding at front.

Use LinkedList::new() to create a new list and push_front to add at the front.

5fill in blank

hard

Fill all three blanks to create a vector, add elements, and access the first element safely.

DSA Rust

let mut vec = Vec::[1]();
vec.[2](5);
let first = vec.[3](0);

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

Anew

Bpush

Cget

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using insert instead of push to add elements.

Using indexing instead of get for safe access.

Create a vector with new(), add elements with push(), and access safely with get().

Practice

1. Which data structure is better when you need fast random access to elements by index?

easy

A. Queue

B. Array

C. Stack

D. Linked List

Solution

1. Step 1: Understand random access in arrays

   Arrays store elements in contiguous memory, so accessing any element by index is fast and direct.

2. Step 2: Compare with linked lists

   Linked lists require traversal from the head to reach an element, making random access slower.

3. Final Answer:

   Array -> Option B

4. Quick Check:

   Random access = Array [OK]

Hint: For fast index access, choose arrays [OK]

Common Mistakes:

• Thinking linked lists allow fast random access
• Confusing stacks or queues with arrays
• Assuming linked lists store elements contiguously

2. Which of the following is the correct Rust syntax to declare a mutable vector (dynamic array)?

easy

A. let mut v = vec[];

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

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

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

Solution

1. Step 1: Identify correct mutable vector declaration

   In Rust, 'let mut v = Vec::new();' declares a mutable vector named v.

2. Step 2: Check other options for syntax errors

   let v = Vec::new(); is immutable vector, C has wrong vec syntax, D has incorrect keyword order.

3. Final Answer:

   let mut v = Vec::new(); -> Option C

4. Quick Check:

   Mutable vector syntax = let mut v = Vec::new(); [OK]

Hint: Use 'let mut' before variable for mutability [OK]

Common Mistakes:

• Forgetting 'mut' for mutable vectors
• Using incorrect vec macro syntax
• Placing 'mut' after variable name

3. Consider this Rust code using a linked list from the standard library:

use std::collections::LinkedList;

let mut list = LinkedList::new();
list.push_back(10);
list.push_back(20);
list.push_front(5);

let first = list.pop_front();
println!("{:?}", first);
println!("{:?}", list);

What is the printed output?

medium

A. Some(5)
[10, 20]

B. Some(10)
[5, 20]

C. None
[5, 10, 20]

D. Some(5)
[5, 10, 20]

Solution

1. Step 1: Trace list operations

   Initially empty list. push_back(10) -> [10], push_back(20) -> [10, 20], push_front(5) -> [5, 10, 20].

2. Step 2: pop_front() removes and returns first element

   pop_front() returns Some(5), list becomes [10, 20].

3. Final Answer:

   Some(5) [10, 20] -> Option A

4. Quick Check:

   pop_front returns first element = Some(5) [OK]

Hint: pop_front removes first element from linked list [OK]

Common Mistakes:

• Confusing push_front and push_back order
• Expecting pop_front to return None
• Misreading list contents after operations

4. The following Rust code tries to remove an element from a linked list but causes a compile error:

use std::collections::LinkedList;

let mut list = LinkedList::new();
list.push_back(1);
list.push_back(2);
let removed = list.remove(0);

What is the main reason for the error?

medium

A. LinkedList in Rust does not have a remove method with index parameter

B. You cannot push_back elements into a LinkedList

C. The list must be immutable to remove elements

D. The remove method requires a mutable reference to the element

Solution

1. Step 1: Check LinkedList API in Rust

   Rust's std::collections::LinkedList does not provide a remove method that takes an index.

2. Step 2: Understand error cause

   Trying to call remove(0) causes compile error because such method does not exist.

3. Final Answer:

   LinkedList in Rust does not have a remove method with index parameter -> Option A

4. Quick Check:

   LinkedList remove by index = no method [OK]

Hint: Rust LinkedList lacks remove by index method [OK]

Common Mistakes:

• Assuming LinkedList supports remove by index
• Confusing mutability rules
• Thinking push_back is invalid

5. You need to store a large collection of elements where insertions and deletions happen frequently at both ends, but you also need to access elements by index occasionally. Which data structure is the best choice in Rust?

hard

A. LinkedList

B. HashMap

C. Vec (Array)

D. VecDeque

Solution

1. Step 1: Analyze requirements for insertions/deletions at both ends

   LinkedList and VecDeque both support fast insertions/removals at front and back.

2. Step 2: Consider occasional index access

   LinkedList has slow index access (O(n)), VecDeque supports efficient indexing (O(1) amortized).

3. Step 3: Compare Vec and HashMap

   Vec has slow front insertions, HashMap is for key-value, not ordered sequence.

4. Final Answer:

   VecDeque -> Option D

5. Quick Check:

   Fast ends + index access = VecDeque [OK]

Hint: Use VecDeque for fast ends and index access [OK]

Common Mistakes:

• Choosing LinkedList despite slow index access
• Choosing Vec despite slow front insertions
• Confusing HashMap with sequence structures