Switch statement power in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Switch with tuple pattern matching

What is the output of this Swift code using a switch statement with tuple pattern matching?

Swift

let point = (2, -2)
switch point {
case (let x, let y) where x == y:
    print("On the line x == y")
case (let x, let y) where x == -y:
    print("On the line x == -y")
default:
    print("Just a point")
}

A On the line x == y

B Just a point

C Compilation error

D On the line x == -y

💡 Hint

Check the conditions in the where clauses carefully.

The tuple (2, -2) matches the second case because 2 == -(-2) is true, so it prints "On the line x == -y".

❓ Predict Output

intermediate

Switch with value binding and fallthrough

What will be printed when this Swift code runs?

Swift

let number = 3
switch number {
case 1:
    print("One")
case 2, 3:
    print("Two or Three")
    fallthrough
case 4:
    print("Four")
default:
    print("Other")
}

A

Two or Three
Four

B Two or Three

C Four

D Other

💡 Hint

Remember what fallthrough does in Swift switch statements.

The case 3 matches and prints "Two or Three", then fallthrough causes the next case (4) to execute, printing "Four".

🔧 Debug

advanced

Why does this switch cause a compile error?

This Swift code causes a compile error. What is the reason?

Swift

let value = 5
switch value {
case 1..<5:
    print("Less than 5")
case 5:
    print("Equal to 5")
case 6...10:
    print("Between 6 and 10")
default: 
    print("Other")
}

A The case _: syntax is invalid; it should be default.

B The range 1..<5 overlaps with 5 causing ambiguity.

C The switch cases are not exhaustive.

D The case _: is unreachable because previous cases cover all values.

💡 Hint

Check the syntax for the default case in Swift switch statements.

Swift requires the default case to be written as 'default:', not 'case _:'. Using 'case _:' causes a syntax error.

❓ Predict Output

advanced

Switch with multiple patterns and where clause

What is the output of this Swift code?

Swift

let char: Character = "e"
switch char {
case "a", "e", "i", "o", "u" where char.isLowercase:
    print("Lowercase vowel")
case "A", "E", "I", "O", "U":
    print("Uppercase vowel")
default:
    print("Consonant")
}

A Lowercase vowel

B Uppercase vowel

C Compilation error

D Consonant

💡 Hint

Check the placement of the where clause with multiple patterns.

In Swift, a where clause cannot be applied to multiple patterns combined with commas. This causes a compile error.

❓ Predict Output

expert

Switch with enum and associated values

Given this Swift enum and switch, what will be printed?

Swift

enum Result {
    case success(Int)
    case failure(String)
}

let result = Result.success(42)
switch result {
case .success(let code) where code > 40:
    print("Success with code > 40")
case .success:
    print("Success with code <= 40")
case .failure(let message):
    print("Failure: \(message)")
}

A Success with code <= 40

B Success with code > 40

C Failure: 42

D Compilation error

💡 Hint

Look at the associated value and the where clause condition.

The enum case is success with associated value 42, which is greater than 40, so the first case matches and prints "Success with code > 40".

Practice

1. What is the main advantage of using a switch statement in Swift compared to multiple if-else statements?

easy

A. It runs faster than any other conditional statement.

B. It makes the code easier to read and maintain by clearly checking many cases.

C. It allows only numeric comparisons.

D. It automatically handles errors without extra code.

Solution

1. Step 1: Understand the purpose of switch

   The switch statement is designed to check a value against multiple cases clearly and cleanly.

2. Step 2: Compare with if-else statements

   While if-else can do similar checks, switch improves readability and maintenance by organizing cases neatly.

3. Final Answer:

   It makes the code easier to read and maintain by clearly checking many cases. -> Option B

4. Quick Check:

   Switch improves readability = A [OK]

Hint: Switch organizes multiple checks clearly for easy reading [OK]

Common Mistakes:

• Thinking switch is always faster than if-else
• Believing switch only works with numbers
• Assuming switch handles errors automatically

2. Which of the following is the correct syntax for a basic switch statement in Swift?

easy

A. switch (value) { case 1 print("One") else print("Other") }

B. switch value { if case 1: print("One") else: print("Other") }

C. switch value: case 1 -> print("One") else -> print("Other")

D. switch value { case 1: print("One") default: print("Other") }

Solution

1. Step 1: Review correct switch syntax

   In Swift, a switch statement uses curly braces with cases followed by colons and code blocks.

2. Step 2: Identify the correct option

   switch value { case 1: print("One") default: print("Other") } matches the correct syntax: switch value { case 1: ... default: ... }.

3. Final Answer:

   switch value { case 1: print("One") default: print("Other") } -> Option D

4. Quick Check:

   Correct switch syntax = B [OK]

Hint: Remember: cases end with colon and use curly braces [OK]

Common Mistakes:

• Omitting colons after case labels
• Using else instead of default
• Wrong punctuation like arrows or missing braces

3. What will be the output of the following Swift code?

let number = 3
switch number {
 case 1, 3, 5:
   print("Odd")
 case 2, 4, 6:
   print("Even")
 default:
   print("Unknown")
}

medium

A. Odd

B. Even

C. Unknown

D. No output

Solution

1. Step 1: Check the value of number

   The variable number is set to 3.

2. Step 2: Match number in switch cases

   Case 1, 3, 5 matches number 3, so it prints "Odd".

3. Final Answer:

   Odd -> Option A

4. Quick Check:

   3 in (1,3,5) = Odd [OK]

Hint: Look for matching case values separated by commas [OK]

Common Mistakes:

• Choosing Even because 3 is odd but not in even case
• Ignoring multiple values in one case
• Assuming default runs when a case matches

4. Identify the error in this Swift switch statement:

let grade = "B"
switch grade {
 case "A":
   print("Excellent")
 case "B"
   print("Good")
 default:
   print("Needs Improvement")
}

medium

A. Switch cannot use strings

B. Missing default case

C. Missing colon after case "B"

D. Print statements must be outside switch

Solution

1. Step 1: Check syntax of each case

   Each case label must end with a colon (:). The case "B" is missing this colon.

2. Step 2: Confirm other parts are correct

   Default case exists, strings are allowed, and print inside switch is valid.

3. Final Answer:

   Missing colon after case "B" -> Option C

4. Quick Check:

   Case labels need colon = C [OK]

Hint: Every case line ends with a colon : [OK]

Common Mistakes:

• Forgetting colon after case label
• Thinking default is optional (it is recommended)
• Believing switch can't handle strings

5. You want to categorize an integer score into grades using a switch statement:
- 90 to 100: "A"
- 80 to 89: "B"
- 70 to 79: "C"
- Below 70: "F"
Which switch statement correctly implements this?

hard

A. switch score {
case 90...100: print("A")
case 80...89: print("B")
case 70...79: print("C")
default: print("F")
}

B. switch score {
case 90..<100: print("A")
case 80..<90: print("B")
case 70..<80: print("C")
default: print("F")
}

C. switch score {
case 90...100: print("A")
case 80...90: print("B")
case 70...80: print("C")
default: print("F")
}

D. switch score {
case 90...100: print("A")
case 80...89: print("B")
case 70...79: print("C")
case 0...69: print("F")
}

Solution

1. Step 1: Understand range operators

   Closed range operator (...) includes both ends, so 90...100 includes 90 and 100.

2. Step 2: Check all ranges cover scores without overlap or gaps

   switch score { case 90...100: print("A") case 80...89: print("B") case 70...79: print("C") default: print("F") } uses closed ranges for exact matches (90-100, 80-89, 70-79) and default catches below 70 perfectly without gaps or overlaps.

3. Step 3: Identify issues in other options

   B uses half-open ranges (..<) excluding upper bounds like 100 (90..<100 misses 100); C has overlapping ranges (80...90 overlaps 90 with A, 70...80 overlaps 80); D lacks default and doesn't cover all integers (e.g., negatives, >100), causing compile error.

4. Final Answer:

   switch score { case 90...100: print("A") case 80...89: print("B") case 70...79: print("C") default: print("F") } -> Option A

5. Quick Check:

   Complete, non-overlapping ranges = A [OK]

Hint: Use closed ranges and cover all values explicitly [OK]

Common Mistakes:

• Overlapping or missing ranges
• Using half-open ranges that exclude max values
• Not covering all possible values explicitly