For loop in Rust - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print each number from 1 to 3.

Rust

for [1] in 1..4 {
    println!("{}", [1]);
}

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

Ai

Bval

Cx

Dnum

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that is not consistent inside the loop.

Using a variable name that is a Rust keyword.

The variable num is used as the loop variable to iterate over the range 1..4.

2fill in blank

medium

Complete the code to sum numbers from 1 to 5 using a for loop.

Rust

let mut sum = 0;
for [1] in 1..6 {
    sum += [1];
}
println!("Sum: {}", sum);

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

Ai

Bx

Cnum

Dval

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different variable name inside the loop body.

Forgetting to declare sum as mutable.

The variable i is used as the loop variable to add each number to sum.

3fill in blank

hard

Fix the error in the for loop to print each element in the vector.

Rust

let numbers = vec![10, 20, 30];
for [1] in &numbers {
    println!("{}", [1]);
}

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

Anumbers

Bi

Cnum

Dval

Attempts:

3 left

💡 Hint

Common Mistakes

Using the vector name as the loop variable.

Not using a reference to the vector.

The loop variable num iterates over references to elements in the vector numbers.

4fill in blank

hard

Fill both blanks to create a for loop that prints even numbers from 2 to 10.

Rust

for [1] in (2..11).step_by([2]) {
    println!("{}", [1]);
}

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

Anum

B2

Ci

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong step value.

Using a loop variable name that conflicts with other variables.

The variable num iterates over the range stepping by 2 to print even numbers.

5fill in blank

hard

Fill all three blanks to create a for loop that prints the squares of numbers from 1 to 5.

Rust

for [1] in 1..6 {
    let square = [2] [3] [2];
    println!("{}", square);
}

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

Ax

C**

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using the ** operator, which does not exist in Rust.

Using different variable names inside and outside the loop.

The loop variable x is used to calculate the square using multiplication x * x.

Practice

1. What does a for loop do in Rust?

easy

A. Declares a variable

B. Defines a new function

C. Repeats actions for each item in a collection

D. Stops the program immediately

Solution

1. Step 1: Understand the purpose of a for loop

   A for loop runs code repeatedly for each item in a list or range.

2. Step 2: Match the description to the options

   Only Repeats actions for each item in a collection describes repeating actions over items in a collection.

3. Final Answer:

   Repeats actions for each item in a collection -> Option C

4. Quick Check:

   For loop = repeat over items [OK]

Hint: For loops repeat actions over collections [OK]

Common Mistakes:

• Confusing for loop with function definition
• Thinking for loop declares variables
• Believing for loop stops program

2. Which of these is the correct syntax for a for loop iterating over numbers 1 to 3 in Rust?

easy

A. for i = 1 to 3 { println!("{}", i); }

B. for i in 1..=3 { println!("{}", i); }

C. for (i in 1..3) println!("{}", i);

D. for i in range(1,3) { println!("{}", i); }

Solution

1. Step 1: Recall Rust for loop syntax

   Rust uses for variable in range { } with ranges like 1..=3 to include 3.

2. Step 2: Check each option

   for i in 1..=3 { println!("{}", i); } uses correct Rust syntax with inclusive range. Others use invalid syntax or functions not in Rust.

3. Final Answer:

   for i in 1..=3 { println!("{}", i); } -> Option B

4. Quick Check:

   Rust for loop uses in and ranges [OK]

Hint: Use 'for var in start..=end' for inclusive ranges [OK]

Common Mistakes:

• Using 'to' instead of 'in' keyword
• Using parentheses around loop variable
• Using Python or other language range syntax

3. What is the output of this Rust code?

let mut sum = 0;
for i in 1..4 {
    sum += i;
}
println!("{}", sum);

medium

A. 6

B. 10

C. 9

D. 7

Solution

1. Step 1: Identify the loop range and iterations

   The loop runs for i = 1, 2, 3 because 1..4 excludes 4.

2. Step 2: Calculate the sum of iterations

   sum = 0 + 1 + 2 + 3 = 6

3. Final Answer:

   6 -> Option A

4. Quick Check:

   1+2+3 = 6 [OK]

Hint: Remember range excludes the end number [OK]

Common Mistakes:

• Including 4 in the sum
• Starting sum at 1 instead of 0
• Confusing inclusive and exclusive ranges

4. Find the error in this Rust for loop code:

for i in 0..5
    println!("{}", i);
}

medium

A. Variable i is not declared

B. Range syntax is incorrect

C. println! macro is used incorrectly

D. Missing curly braces around loop body

Solution

1. Step 1: Check loop syntax

   Rust requires curly braces { } around the loop body if it has more than one statement or to be explicit.

2. Step 2: Identify the missing brace

   The code has a closing brace '}' without an opening brace '{' before println!().

3. Final Answer:

   Missing curly braces around loop body -> Option D

4. Quick Check:

   For loop body needs braces [OK]

Hint: Always use braces {} for loop bodies [OK]

Common Mistakes:

• Forgetting opening brace
• Assuming range syntax is wrong
• Thinking variable needs declaration outside loop

5. How can you use a for loop in Rust to print only even numbers from 2 to 10 inclusive?

hard

A. for i in 2..=10 { if i % 2 == 0 { println!("{}", i); } }

B. for i in 2..10 { if i % 2 = 0 { println!("{}", i); } }

C. for i in 2..=10 { if i / 2 == 0 { println!("{}", i); } }

D. for i in 2..=10 { if i % 2 != 0 { println!("{}", i); } }

Solution

1. Step 1: Understand the range and condition

   We want numbers from 2 to 10 inclusive, so use 2..=10. To print even numbers, check if remainder when divided by 2 is zero.

2. Step 2: Check each option's condition

   for i in 2..=10 { if i % 2 == 0 { println!("{}", i); } } correctly uses i % 2 == 0. for i in 2..10 { if i % 2 = 0 { println!("{}", i); } } uses assignment (=) instead of comparison (==). for i in 2..=10 { if i / 2 == 0 { println!("{}", i); } } uses division instead of modulo. for i in 2..=10 { if i % 2 != 0 { println!("{}", i); } } prints odd numbers.

3. Final Answer:

   for i in 2..=10 { if i % 2 == 0 { println!("{}", i); } } -> Option A

4. Quick Check:

   Use modulo == 0 for even check [OK]

Hint: Use 'if i % 2 == 0' inside for loop [OK]

Common Mistakes:

• Using '=' instead of '==' in condition
• Using division instead of modulo
• Printing odd numbers by mistake