Memory Layout Comparison Array vs Linked List in DSA Rust - Interactive Comparison Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a fixed-size array of 5 integers in Rust.

DSA Rust

let numbers: [i32; [1]] = [1, 2, 3, 4, 5];

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

A6

B4

C5

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using a size smaller or larger than the number of elements.

The array size must match the number of elements. Here, 5 elements require size 5.

2fill in blank

medium

Complete the code to create a linked list node struct with a value and a next pointer.

DSA Rust

struct Node {
    value: i32,
    next: Option<Box<[1]>>,
}

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

ANode

BOption

CVec<i32>

Di32

Attempts:

3 left

💡 Hint

Common Mistakes

Using primitive types or collections instead of the struct name.

The next pointer must point to the same Node type wrapped in Box and Option for linked list.

3fill in blank

hard

Fix the error in the code to correctly create a linked list node with value 10 and no next node.

DSA Rust

let node = Node {
    value: 10,
    next: [1],
};

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

ABox::new(Node { value: 10, next: None })

BBox::new(None)

CSome(10)

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Using Some or Box::new(None) incorrectly.

The next field is an Option>, so None means no next node.

4fill in blank

hard

Fill both blanks to create a vector and access its first element safely.

DSA Rust

let numbers = Vec::new();
numbers.push(1);
let first = numbers.[1]().[2]();

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

Aget

Bunwrap

Cpop

Dfirst

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop removes the element, get returns Option<&T> but needs index.

Use first() to get an Option reference to the first element, then unwrap() to get the value.

5fill in blank

hard

Fill all three blanks to create a linked list node with value 5 and next node with value 10.

DSA Rust

let second = Node {
    value: [1],
    next: None,
};
let first = Node {
    value: [2],
    next: Some(Box::new([3])),
};

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

A5

B10

Csecond

Dfirst

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up values or next pointers.

The second node has value 10 and no next. The first node has value 5 and points to second.

Practice

1. Which statement best describes the memory layout difference between an array and a linked list?

easy

A. A linked list stores elements contiguously, but an array uses pointers between elements.

B. Both array and linked list store elements contiguously in memory.

C. Arrays use pointers to link elements, linked lists store elements contiguously.

D. An array stores elements contiguously in memory, while a linked list stores elements scattered with pointers.

Solution

1. Step 1: Understand array memory layout

   An array stores all its elements in a continuous block of memory, so elements are next to each other.

2. Step 2: Understand linked list memory layout

   A linked list stores each element separately in memory, and each element has a pointer to the next, so elements are scattered.

3. Final Answer:

   An array stores elements contiguously in memory, while a linked list stores elements scattered with pointers. -> Option D

4. Quick Check:

   Array = contiguous, Linked list = scattered with pointers [OK]

Hint: Arrays are continuous blocks; linked lists use pointers [OK]

Common Mistakes:

• Thinking linked lists store elements contiguously
• Confusing pointers usage between arrays and linked lists
• Assuming arrays use pointers between elements

2. Which Rust code snippet correctly declares a fixed-size array of 5 integers with explicit type annotation?

easy

A. let arr = [1, 2, 3, 4, 5];

B. let arr = vec![1, 2, 3, 4, 5];

C. let arr: [i32; 5] = [1, 2, 3, 4, 5];

D. let arr = (1, 2, 3, 4, 5);

Solution

1. Step 1: Identify fixed-size array syntax in Rust

   Rust fixed-size arrays require type and size: [type; size].

2. Step 2: Check each option

   let arr: [i32; 5] = [1, 2, 3, 4, 5]; uses let arr: [i32; 5] = [1, 2, 3, 4, 5]; which is correct fixed-size array syntax.

3. Final Answer:

   let arr: [i32; 5] = [1, 2, 3, 4, 5]; -> Option C

4. Quick Check:

   Fixed-size array syntax = [type; size] [OK]

Hint: Fixed arrays need type and size: [type; size] [OK]

Common Mistakes:

• Using vec! macro for fixed-size array
• Missing type and size in array declaration
• Using tuple syntax instead of array

3. Consider this Rust code creating a linked list node struct and two nodes linked together:

struct Node {
    value: i32,
    next: Option,
}

fn main() {
    let node2 = Node { value: 20, next: None };
    let node1 = Node { value: 10, next: Some(Box::new(node2)) };
    println!("{} -> {} -> None", node1.value, node1.next.as_ref().unwrap().value);
}

What is the printed output?

medium

A. 10 -> 20 -> None

B. 20 -> 10 -> None

C. 10 -> None -> None

D. Compilation error due to ownership

Solution

1. Step 1: Understand node creation and linking

   node2 has value 20 and no next node. node1 has value 10 and points to node2 via Box.

2. Step 2: Trace the print statement

   Prints node1.value (10), then node1.next's value (20), then "None" for end.

3. Final Answer:

   10 -> 20 -> None -> Option A

4. Quick Check:

   Linked nodes print values in order: 10 then 20 [OK]

Hint: Follow pointers to print linked list values [OK]

Common Mistakes:

• Confusing order of nodes
• Expecting None printed as value
• Thinking ownership causes compile error here

4. This Rust code tries to create a linked list but fails to compile:

struct Node {
    value: i32,
    next: Option,
}

fn main() {
    let node1 = Node { value: 10, next: None };
    let node2 = Node { value: 20, next: Some(Box::new(node1)) };
    println!("{} -> {} -> None", node1.value, node2.value);
}

What is the main reason for the compilation error?

medium

A. Use of moved value: node1 is moved into node2 and cannot be used again

B. Missing lifetime annotations on struct Node

C. Box cannot be used inside Option

D. Printing node2.value is invalid syntax

Solution

1. Step 1: Analyze ownership of node1

   node1 is moved into Box inside node2's next field, so node1 cannot be used after move.

2. Step 2: Identify error cause

   Because node1 is moved, any further use or move causes compile error "use of moved value".

3. Final Answer:

   Use of moved value: node1 is moved into node2 and cannot be used again -> Option A

4. Quick Check:

   Ownership moved node1 causes compile error [OK]

Hint: Moving ownership invalidates original variable [OK]

Common Mistakes:

• Thinking Box inside Option is invalid
• Assuming missing lifetimes cause error here
• Believing print syntax is wrong

5. You want to store 1 million integers and frequently access elements by index. Considering memory layout and performance, which data structure is better in Rust and why?

hard

A. Array, because linked lists cannot store integers efficiently.

B. Array, because elements are stored contiguously allowing fast index access and better cache usage.

C. Linked list, because it uses less memory than arrays for large data.

D. Linked list, because it uses pointers and is faster for random access.

Solution

1. Step 1: Consider access pattern and memory layout

   Arrays store elements contiguously, so accessing by index is O(1) and cache-friendly.

2. Step 2: Compare linked list access and memory use

   Linked lists store elements scattered with pointers, making index access O(n) and less cache efficient.

3. Final Answer:

   Array, because elements are stored contiguously allowing fast index access and better cache usage. -> Option B

4. Quick Check:

   Contiguous arrays = fast index access [OK]

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

Common Mistakes:

• Assuming linked lists are faster for index access
• Thinking linked lists use less memory for large data
• Believing arrays cannot store large data efficiently