Stride for custom step in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of stride with positive step

What is the output of this Swift code using stride with a positive step?

Swift

for number in stride(from: 2, to: 10, by: 3) {
    print(number, terminator: " ")
}

A 2 5 8

B 2 3 4 5 6 7 8 9

C 2 6 10

D 3 6 9

💡 Hint

Remember that 'to' excludes the upper bound and the step is 3.

The stride starts at 2 and adds 3 each time: 2, 5, 8. It stops before reaching 10.

❓ Predict Output

intermediate

Output of stride with negative step

What is the output of this Swift code using stride with a negative step?

Swift

for number in stride(from: 10, through: 2, by: -4) {
    print(number, terminator: " ")
}

A 10 6 2

B 10 6

C 10 8 6 4 2

D 10 2

💡 Hint

The 'through' keyword includes the end value, and step is negative.

Starting at 10, subtract 4 each time: 10, 6, 2. The loop includes 2 because of 'through'.

🧠 Conceptual

advanced

Behavior of stride with zero step

What happens if you use stride(from: 1, to: 10, by: 0) in Swift?

A The loop does not run at all.

B The program runs an infinite loop printing 1 endlessly.

C The program throws a runtime error due to zero step.

D The loop runs once printing 1 and stops.

💡 Hint

Think about what happens when the step never changes the value.

A zero step causes a runtime error because the step must not be zero.

❓ Predict Output

advanced

Count of elements generated by stride

How many numbers does this Swift stride generate?

Swift

let numbers = Array(stride(from: 0, to: 20, by: 7))
print(numbers.count)

A 4

B 3

C 2

D 5

💡 Hint

Count the numbers starting at 0, adding 7 each time, stopping before 20.

The numbers are 0, 7, 14. The next would be 21 which is beyond 20, so count is 3.

❓ Predict Output

expert

Output of stride with floating point step

What is the output of this Swift code using stride with a floating point step?

Swift

for value in stride(from: 0.0, through: 1.0, by: 0.3) {
    print(String(format: "%.1f", value), terminator: " ")
}

A 0.0 0.3 0.6 0.9 1.2

B 0.0 0.3 0.6 0.9 1.1

C 0.0 0.3 0.6 0.9 1.0

D 0.0 0.3 0.6 0.9

💡 Hint

'through' includes the end value only if exactly reachable by the steps; consider floating-point.

The stride generates 0.0, 0.3, 0.6, 0.9. The next value 1.2 exceeds 1.0, and 1.0 is not exactly reached.