For-in loop with ranges in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a for-in loop with a closed range

What is the output of this Swift code?

for i in 1...3 {
    print(i, terminator: " ")
}

Swift

for i in 1...3 {
    print(i, terminator: " ")
}

A 1 2 3

B 1 2

C 0 1 2 3

D 2 3 4

💡 Hint

The closed range operator '...' includes both the start and end values.

The for-in loop iterates over the range 1 to 3 inclusive, printing each number with a space.

❓ Predict Output

intermediate

Output of a for-in loop with a half-open range

What does this Swift code print?

for i in 0..<4 {
    print(i, terminator: ",")
}

Swift

for i in 0..<4 {
    print(i, terminator: ",")
}

A 0,1,2,

B 0,1,2,3,4,

C 1,2,3,4,

D 0,1,2,3,

💡 Hint

The half-open range operator '..<' excludes the upper bound.

The loop runs from 0 up to but not including 4, printing each number followed by a comma.

🔧 Debug

advanced

Identify the error in the for-in loop with range

What error does this Swift code produce?

for i in 1...5 {
    if i = 3 {
        print("Three")
    }
}

Swift

for i in 1...5 {
    if i == 3 {
        print("Three")
    }
}

A Syntax error: Cannot assign to value: 'i' is a 'let' constant

B Runtime error: Index out of range

C Syntax error: Expected '==' in conditional

D No error, prints 'Three' once

💡 Hint

Check the condition inside the if statement for correct comparison syntax.

The code uses '=' which is assignment, but in conditions you must use '==' for comparison.

🧠 Conceptual

advanced

Number of iterations in a for-in loop with stride

How many times does this Swift loop run?

for i in stride(from: 0, to: 10, by: 3) {
    print(i)
}

Swift

for i in stride(from: 0, to: 10, by: 3) {
    print(i)
}

A 10 times

B 4 times

C 5 times

D 3 times

💡 Hint

The stride goes from 0 up to but not including 10, stepping by 3 each time.

The values are 0, 3, 6, 9 — four iterations before reaching 10.

❓ Predict Output

expert

Output of nested for-in loops with ranges

What is the output of this Swift code?

for i in 1...2 {
    for j in 1...2 {
        print(i * j, terminator: " ")
    }
}

Swift

for i in 1...2 {
    for j in 1...2 {
        print(i * j, terminator: " ")
    }
}

A 1 2 2 4

B 1 1 2 2

C 2 4 1 2

D 1 2 3 4

💡 Hint

Multiply each pair of i and j values in the nested loops.

The outer loop runs i=1,2; inner loop runs j=1,2; products are 1*1=1, 1*2=2, 2*1=2, 2*2=4.