Stride for custom step in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a stride from 0 to 10 with a step of 2.

Swift

for number in stride(from: 0, to: 10, by: [1]) {
    print(number)
}

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

A2

B5

C1

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using a step larger than the range, which results in fewer numbers.

Using 'to' instead of 'through' when you want to include the end number.

The stride(from:to:by:) function creates a sequence starting at 0, up to but not including 10, stepping by 2.

2fill in blank

medium

Complete the code to create a stride from 1 through 9 with a step of 2.

Swift

for number in stride(from: 1, through: 9, by: [1]) {
    print(number)
}

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

A2

B3

C4

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'to' instead of 'through' which excludes the last number.

Using a step that skips the last number.

Using stride(from:through:by:) with step 2 includes the last number 9 if it fits the sequence.

3fill in blank

hard

Fix the error in the stride to count down from 10 to 0 by 2.

Swift

for number in stride(from: 10, through: 0, by: [1]) {
    print(number)
}

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

A-1

B2

C-2

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a positive step when counting down causes an infinite loop or no output.

Using -1 instead of -2 changes the step size.

When counting down, the step must be negative. Here, -2 counts down by 2.

4fill in blank

hard

Fill both blanks to create a stride from 5 to 15 with a step of 3.

Swift

for number in stride(from: [1], to: [2], by: 3) {
    print(number)
}

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

A5

B10

C15

D20

Attempts:

3 left

💡 Hint

Common Mistakes

Using 15 as the end excludes numbers up to 15.

Using 'through' instead of 'to' changes the inclusion of the end number.

The stride starts at 5 and goes up to but not including 10, stepping by 3.

5fill in blank

hard

Fill all three blanks to create a stride from 20 down to 10 with a step of 2.

Swift

for number in stride(from: [1], through: [2], by: [3]) {
    print(number)
}

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

A20

B10

C-2

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using a positive step when counting down.

Using 'to' instead of 'through' to include the end number.

The stride counts down from 20 through 10 by steps of -2.

Practice

1. What does the Swift function stride(from: 1, to: 10, by: 2) do?

easy

A. Generates numbers starting at 1, decreasing by 2, up to but not including 10.

B. Generates numbers starting at 1, increasing by 2, including 10.

C. Generates numbers starting at 1, increasing by 2, up to but not including 10.

D. Generates numbers starting at 1, decreasing by 2, including 10.

Solution

1. Step 1: Understand the parameters of stride

   The function uses from: 1 as the start, to: 10 as the end (exclusive), and by: 2 as the step size.

2. Step 2: Determine the sequence generated

   It generates numbers starting at 1, adding 2 each time, stopping before reaching 10, so the sequence is 1, 3, 5, 7, 9.

3. Final Answer:

   Generates numbers starting at 1, increasing by 2, up to but not including 10. -> Option C

4. Quick Check:

   stride(from:1, to:10, by:2) excludes 10 [OK]

Hint: Remember: 'to' excludes the end value in stride [OK]

Common Mistakes:

• Confusing 'to' with 'through' and including the end value
• Mixing up positive and negative step directions
• Assuming the step is always 1

2. Which of the following is the correct syntax to create a stride in Swift that counts down from 10 to 2 by steps of 2, including 2?

easy

A. stride(from: 10, through: 2, by: -2)

B. stride(from: 10, to: 2, by: -2)

C. stride(from: 2, through: 10, by: 2)

D. stride(from: 2, to: 10, by: 2)

Solution

1. Step 1: Identify counting down with inclusion

   Counting down from 10 to 2 means the step is negative (-2). Including 2 means using through.

2. Step 2: Match syntax to requirements

   Only stride(from: 10, through: 2, by: -2) matches counting down with inclusion of 2.

3. Final Answer:

   stride(from: 10, through: 2, by: -2) -> Option A

4. Quick Check:

   Use 'through' to include end, negative step for countdown [OK]

Hint: Use 'through' to include end; negative step for countdown [OK]

Common Mistakes:

• Using 'to' instead of 'through' when including the end
• Using positive step when counting down
• Swapping start and end values

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

for i in stride(from: 0, to: 5, by: 2) {
    print(i)
}

medium

A. 0 2 4

B. 0 2 4 6

C. 0 2 4 5

D. 2 4

Solution

1. Step 1: Analyze the stride parameters

   The loop starts at 0, goes up to but excludes 5, stepping by 2.

2. Step 2: List the values printed

   Values are 0, 2, 4. It stops before reaching 5.

3. Final Answer:

   0 2 4 -> Option A

4. Quick Check:

   Stride 'to' excludes end, so 5 is not printed [OK]

Hint: Remember 'to' excludes end value in stride loops [OK]

Common Mistakes:

• Including the end value 5 mistakenly
• Adding an extra step beyond the end
• Confusing step size with end value

4. Identify the error in this Swift code snippet:

for i in stride(from: 1, through: 10, by: 0) {
    print(i)
}

medium

A. Using 'through' instead of 'to' is invalid syntax.

B. Step value cannot be zero; it causes a runtime error.

C. Start value must be less than end value for positive step.

D. The loop will run infinitely without errors.

Solution

1. Step 1: Check the step parameter

   The step is zero, which is invalid because it causes no progress in the loop.

2. Step 2: Understand the effect of zero step

   A zero step causes a runtime error or infinite loop because the loop never advances.

3. Final Answer:

   Step value cannot be zero; it causes a runtime error. -> Option B

4. Quick Check:

   Step must not be zero in stride [OK]

Hint: Step cannot be zero; always non-zero positive or negative [OK]

Common Mistakes:

• Thinking 'through' is invalid syntax
• Assuming zero step means step of 1
• Ignoring runtime errors caused by zero step

5. You want to create a Swift loop that prints all odd numbers from 1 to 15 inclusive, but only those greater than 5. Which stride and condition combination achieves this?

hard

A. for i in stride(from: 1, to: 15, by: 2) { if i >= 5 { print(i) } }

B. for i in stride(from: 5, to: 15, by: 2) { print(i) }

C. for i in stride(from: 1, through: 15, by: 2) { if i >= 5 { print(i) } }

D. for i in stride(from: 1, through: 15, by: 2) { if i > 5 { print(i) } }

Solution

1. Step 1: Identify stride to generate odd numbers 1 to 15 inclusive

   Using stride(from: 1, through: 15, by: 2) generates 1,3,5,...,15 including 15.

2. Step 2: Filter numbers greater than 5

   The condition if i > 5 prints only numbers greater than 5, i.e., 7,9,11,13,15.

3. Final Answer:

   for i in stride(from: 1, through: 15, by: 2) { if i > 5 { print(i) } } -> Option D

4. Quick Check:

   Stride with 'through' includes 15; condition filters >5 [OK]

Hint: Use 'through' to include end; filter inside loop for conditions [OK]

Common Mistakes:

• Using 'to' excludes 15, missing last number
• Incorrect condition filtering numbers equal to 5
• Starting stride at 5 misses odd numbers less than 5