Vector vs array comparison in Rust - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a vector with three integers.

Rust

let numbers = Vec::[1]([1, 2, 3]);

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

Anew

Bwith_capacity

Cfrom

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using Vec::new() creates an empty vector, not from an array.

Using Vec::push is a method to add elements, not to create a vector.

The Vec::from function creates a vector from an array.

2fill in blank

medium

Complete the code to declare an array of five integers.

Rust

let arr: [i32; 5] = [1];

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

A[1, 2, 3, 4, 5]

B[1, 2, 3]

Cvec![1, 2, 3, 4, 5]

DVec::new()

Attempts:

3 left

💡 Hint

Common Mistakes

Using vec! macro creates a vector, not an array.

Providing fewer or more elements than the declared size causes errors.

An array in Rust is declared with square brackets and a fixed size. Here, five integers are listed.

3fill in blank

hard

Fix the error in comparing a vector and an array for equality.

Rust

let v = vec![1, 2, 3];
let a = [1, 2, 3];
let are_equal = v [1] a;

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

A.eq(

B==

C!=

Dequals

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'equals' is not valid syntax in Rust.

Using '!=' checks for inequality, not equality.

Using '.eq(' without proper syntax causes errors.

In Rust, you can compare a vector and an array directly with == because vectors implement comparison with slices.

4fill in blank

hard

Fill both blanks to create a vector from an array and check if they are equal.

Rust

let arr = [10, 20, 30];
let vec = Vec::[1](arr);
let equal = vec [2] arr;

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

Afrom

B==

C!=

Dnew

Attempts:

3 left

💡 Hint

Common Mistakes

Using Vec::new() creates an empty vector, not from an array.

Using '!=' checks for inequality, not equality.

Vec::from converts an array to a vector, and == compares them for equality.

5fill in blank

hard

Fill all three blanks to create an array, convert it to a vector, and compare their lengths.

Rust

let arr: [i32; 4] = [1];
let vec = Vec::from(arr);
let same_length = vec.[2]() == arr.[3]();

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

A[5, 6, 7, 8]

Blen

D[1, 2, 3]

Attempts:

3 left

💡 Hint

Common Mistakes

Declaring array with wrong number of elements.

Using incorrect method names instead of len().

The array is declared with four elements. Both vector and array have a len() method to get their length for comparison.

Practice

1. Which of the following statements correctly describes the main difference between a Rust array and a Rust vector?

easy

A. Arrays have a fixed size known at compile time, while vectors can grow or shrink at runtime.

B. Vectors have a fixed size known at compile time, while arrays can grow or shrink at runtime.

C. Both arrays and vectors have fixed sizes and cannot change after creation.

D. Arrays are only used for strings, while vectors are used for numbers.

Solution

1. Step 1: Understand array size behavior

   Arrays in Rust have a fixed size that must be known when the program is compiled.

2. Step 2: Understand vector size behavior

   Vectors are dynamic and can grow or shrink during program execution.

3. Final Answer:

   Arrays have a fixed size known at compile time, while vectors can grow or shrink at runtime. -> Option A

4. Quick Check:

   Array fixed size, Vector dynamic size = C [OK]

Hint: Remember: arrays fixed size, vectors flexible size [OK]

Common Mistakes:

• Confusing which type is fixed or dynamic
• Thinking vectors are fixed size
• Assuming arrays can grow dynamically

2. Which of the following is the correct syntax to declare a vector of integers in Rust?

easy

A. let v = (1, 2, 3);

B. let v = [1, 2, 3];

C. let v = vector(1, 2, 3);

D. let v = vec![1, 2, 3];

Solution

1. Step 1: Identify vector creation syntax

   In Rust, vectors are created using the macro vec![...] with square brackets and exclamation mark.

2. Step 2: Compare options

   let v = vec![1, 2, 3]; uses vec![1, 2, 3], which is correct. let v = [1, 2, 3]; is an array, C and D are invalid syntax for vectors.

3. Final Answer:

   let v = vec![1, 2, 3]; -> Option D

4. Quick Check:

   Vector syntax uses vec! macro = A [OK]

Hint: Vectors use vec! macro with square brackets [OK]

Common Mistakes:

• Using array syntax instead of vec! macro
• Missing exclamation mark in vec! macro
• Using parentheses instead of brackets

3. What will be the output of the following Rust code?

let arr = [10, 20, 30];
let vec = vec![10, 20, 30];
println!("{} {}", arr.len(), vec.len());

medium

A. 3 0

B. 3 3

C. 0 3

D. Compilation error

Solution

1. Step 1: Check array length

   The array arr has 3 elements, so arr.len() returns 3.

2. Step 2: Check vector length

   The vector vec also has 3 elements, so vec.len() returns 3.

3. Final Answer:

   3 3 -> Option B

4. Quick Check:

   Both lengths are 3 = B [OK]

Hint: Both array and vector have length 3 here [OK]

Common Mistakes:

• Assuming vector length is zero initially
• Confusing array and vector length methods
• Expecting compilation error due to different types

4. Identify the error in this Rust code snippet:

let arr = [1, 2, 3];
arr.push(4);

medium

A. Arrays do not have a push method; only vectors do.

B. The array is missing a semicolon after declaration.

C. The push method requires a mutable reference to the array.

D. The code is correct and will compile.

Solution

1. Step 1: Check array methods

   Arrays in Rust have fixed size and do not support the push method.

2. Step 2: Understand push method usage

   The push method is only available for vectors, which are growable.

3. Final Answer:

   Arrays do not have a push method; only vectors do. -> Option A

4. Quick Check:

   push() only works on vectors = D [OK]

Hint: Only vectors support push(), arrays do not [OK]

Common Mistakes:

• Trying to push to arrays
• Thinking arrays can be resized
• Ignoring method availability on types

5. You want to store a list of user scores that can change size during the program. Which Rust type should you choose and why?

hard

A. Use a tuple because it can hold multiple types of scores.

B. Use an array because it is faster and fixed size is better for scores.

C. Use a vector because it can grow or shrink as scores are added or removed.

D. Use a string because scores are numbers stored as text.

Solution

1. Step 1: Analyze data size requirement

   The list of user scores can change size, so a fixed size container is not suitable.

2. Step 2: Choose appropriate Rust type

   Vectors are growable and flexible, making them ideal for dynamic lists like scores.

3. Final Answer:

   Use a vector because it can grow or shrink as scores are added or removed. -> Option C

4. Quick Check:

   Dynamic list needs vector = A [OK]

Hint: Dynamic size needs vector, fixed size needs array [OK]

Common Mistakes:

• Choosing array for dynamic data
• Confusing tuples with lists
• Using string for numeric data