Repeat-while loop in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple repeat-while loop

What is the output of this Swift code using a repeat-while loop?

Swift

var count = 1
repeat {
    print(count)
    count += 1
} while count <= 3

A

1
2
3

B

1
2
3
4

C

2
3
4

D

0
1
2
3

💡 Hint

Remember that repeat-while runs the loop body first, then checks the condition.

The loop starts with count = 1, prints it, then increments. It repeats while count <= 3, so it prints 1, 2, and 3.

❓ Predict Output

intermediate

Repeat-while loop with condition false initially

What will this Swift code print?

Swift

var number = 5
repeat {
    print(number)
    number += 1
} while number < 5

A Error: infinite loop

B 5

C

5
6
7
8...

D No output

💡 Hint

The repeat-while loop runs the body once before checking the condition.

Even though the condition is false at the start, the loop body runs once and prints 5.

🔧 Debug

advanced

Identify the error in this repeat-while loop

What error does this Swift code produce?

Swift

var i = 0
repeat {
    print(i)
    i += 1
} while i = 5

A SyntaxError: Cannot assign to value in condition

B RuntimeError: Infinite loop

C No error, prints 0 to 4

D TypeError: i is not a Boolean

💡 Hint

Check the condition syntax in the while statement.

The condition uses '=' which is assignment, not comparison. Swift requires '==' for comparison, so this causes a syntax error.

🧠 Conceptual

advanced

Repeat-while loop vs while loop behavior

Which statement correctly describes the difference between repeat-while and while loops in Swift?

A repeat-while loops check the condition before executing the body

B Both loops execute the body at least once regardless of condition

C repeat-while executes the loop body at least once; while may not execute if condition is false initially

D while executes the loop body at least once; repeat-while may not execute if condition is false initially

💡 Hint

Think about when the condition is checked in each loop type.

repeat-while runs the body first, then checks the condition, so it always runs at least once. while checks the condition first and may skip the body.

❓ Predict Output

expert

Output of nested repeat-while loops

What is the output of this Swift code with nested repeat-while loops?

Swift

var x = 1
repeat {
    var y = 1
    repeat {
        print("(\(x),\(y))")
        y += 1
    } while y <= 2
    x += 1
} while x <= 2

A

(1,1)
(2,1)
(2,2)

B

(1,1)
(2,1)
(1,2)
(2,2)

C

(1,1)
(1,2)
(1,3)
(2,1)
(2,2)

D

(1,1)
(1,2)
(2,1)
(2,2)

💡 Hint

The inner loop runs fully for each iteration of the outer loop.

For x=1, y runs 1 to 2 printing (1,1) and (1,2). Then x=2, y runs again 1 to 2 printing (2,1) and (2,2).