Switch statement in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a switch statement on variable choice.

C++

switch([1]) {
    case 1:
        // code
        break;
    default:
        // code
}

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

Achoice

B1

Cswitch

Dcase

Attempts:

3 left

💡 Hint

Common Mistakes

Putting a number instead of the variable inside switch parentheses.

Writing 'switch' or 'case' inside the parentheses.

The switch statement requires the variable or expression to check inside parentheses. Here, it should be choice.

2fill in blank

medium

Complete the code to add a case for when choice equals 2.

C++

switch(choice) {
    case [1]:
        std::cout << "Choice is 2" << std::endl;
        break;
    default:
        std::cout << "Other choice" << std::endl;
}

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

A1

B2

Cchoice

Ddefault

Attempts:

3 left

💡 Hint

Common Mistakes

Using the variable name instead of a constant value.

Writing 'default' as a case label.

The case label must be the constant value to match. Here, it is 2.

3fill in blank

hard

Fix the error in the switch statement by completing the missing keyword.

C++

switch(choice) {
    case 1:
        std::cout << "One" << std::endl;
        [1];
    default:
        std::cout << "Default" << std::endl;
}

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

Abreak

Bcontinue

Creturn

Dexit

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting break causes fall-through.

Using continue or return incorrectly inside switch.

The break statement is needed to exit the switch after a case is handled to avoid falling through.

4fill in blank

hard

Fill both blanks to create a switch that prints "Low" for 1 or 2, and "High" for 3.

C++

switch(choice) {
    case [1]:
    case [2]:
        std::cout << "Low" << std::endl;
        break;
    case 3:
        std::cout << "High" << std::endl;
        break;
}

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

A1

B2

C3

Ddefault

Attempts:

3 left

💡 Hint

Common Mistakes

Using default instead of case labels.

Not using break after the shared cases.

Cases 1 and 2 both print "Low" by falling through to the same code block.

5fill in blank

hard

Fill all three blanks to complete a switch that prints the day name for 1, 2, or default.

C++

switch(day) {
    case [1]:
        std::cout << "Monday" << std::endl;
        break;
    case [2]:
        std::cout << "Tuesday" << std::endl;
        break;
    [3]:
        std::cout << "Other day" << std::endl;
}

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

A1

B2

Cdefault

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using numbers instead of default for the last case.

Omitting break statements.

Cases 1 and 2 print Monday and Tuesday, and default handles all other values.

Practice

1. What is the main purpose of a switch statement in C++?

easy

A. To declare a variable

B. To repeat a block of code multiple times

C. To define a function

D. To choose which block of code to run based on a single value

Solution

1. Step 1: Understand the role of switch

   A switch statement checks one value and runs code matching that value.

2. Step 2: Compare with other options

   Repeating code is done by loops, functions define reusable code, and variables store data.

3. Final Answer:

   To choose which block of code to run based on a single value -> Option D

4. Quick Check:

   Switch selects code by value = A [OK]

Hint: Switch picks code based on one value quickly [OK]

Common Mistakes:

• Confusing switch with loops
• Thinking switch defines functions
• Mixing switch with variable declaration

2. Which of the following is the correct syntax to start a switch statement for variable choice?

easy

A. switch(choice) {

B. switch choice {

C. switch choice() {

D. switch(choice);

Solution

1. Step 1: Recall switch syntax

   The switch statement requires parentheses around the variable: switch(variable).

2. Step 2: Check each option

   switch(choice) { uses correct parentheses and opening brace. Others miss parentheses or use wrong punctuation.

3. Final Answer:

   switch(choice) { -> Option A

4. Quick Check:

   Correct switch syntax uses parentheses [OK]

Hint: Switch needs parentheses around variable [OK]

Common Mistakes:

• Omitting parentheses
• Using semicolon instead of brace
• Adding parentheses after variable name

3. What will be the output of this code?

int x = 2;
switch(x) {
  case 1:
    std::cout << "One";
    break;
  case 2:
    std::cout << "Two";
    break;
  default:
    std::cout << "Other";
}

medium

A. One

B. Two

C. Other

D. No output

Solution

1. Step 1: Check the value of x

   The variable x is 2.

2. Step 2: Match case in switch

   The switch matches case 2, so it prints "Two" and then breaks.

3. Final Answer:

   Two -> Option B

4. Quick Check:

   Value 2 matches case 2 = Two [OK]

Hint: Match variable value to case label [OK]

Common Mistakes:

• Forgetting break causes fall-through
• Choosing default when case matches
• Confusing output with case number

4. Identify the error in this switch statement:

int n = 3;
switch(n) {
  case 1:
    std::cout << "One";
  case 2:
    std::cout << "Two";
    break;
  default:
    std::cout << "Default";
}

medium

A. default case must be last

B. Variable n should be a string

C. Missing break after case 1 causes fall-through

D. case labels must be strings

Solution

1. Step 1: Check case 1 block

   There is no break; after case 1, so execution falls through to case 2.

2. Step 2: Understand consequences

   Without break, both "One" and "Two" print if n=1. This is usually unintended.

3. Final Answer:

   Missing break after case 1 causes fall-through -> Option C

4. Quick Check:

   Break prevents fall-through = A [OK]

Hint: Always add break after each case to stop fall-through [OK]

Common Mistakes:

• Forgetting break causes multiple outputs
• Thinking default must be last (it can be anywhere)
• Believing case labels must be strings

5. You want to write a switch statement that prints "Weekend" for cases 6 and 7, and "Weekday" for cases 1 to 5. Which code snippet correctly does this?

hard

A. switch(day) {
case 1: case 2: case 3: case 4: case 5:
std::cout << "Weekday";
break;
case 6: case 7:
std::cout << "Weekend";
break;
default:
std::cout << "Invalid";
}

B. switch(day) {
case 1:
case 2:
case 3:
case 4:
case 5:
std::cout << "Weekend";
break;
case 6:
case 7:
std::cout << "Weekday";
break;
default:
std::cout << "Invalid";
}

C. switch(day) {
case 1:
case 2:
case 3:
case 4:
case 5:
std::cout << "Weekday";
case 6:
case 7:
std::cout << "Weekend";
break;
default:
std::cout << "Invalid";
}

D. switch(day) {
case 1: case 2: case 3: case 4: case 5:
std::cout << "Weekend";
case 6: case 7:
std::cout << "Weekday";
break;
default:
std::cout << "Invalid";
}

Solution

1. Step 1: Group cases for weekdays and weekends

   Cases 1 to 5 print "Weekday"; cases 6 and 7 print "Weekend". Grouping cases with no code between them is correct.

2. Step 2: Check breaks and outputs

   switch(day) { case 1: case 2: case 3: case 4: case 5: std::cout << "Weekday"; break; case 6: case 7: std::cout << "Weekend"; break; default: std::cout << "Invalid"; } groups cases correctly and uses breaks to prevent fall-through. Others mix outputs or miss breaks.

3. Final Answer:

   Option A code correctly prints "Weekday" for 1-5 and "Weekend" for 6-7 -> Option A

4. Quick Check:

   Group cases + breaks = correct switch [OK]

Hint: Group cases without code, add break after each group [OK]

Common Mistakes:

• Missing breaks causing fall-through
• Swapping outputs for cases
• Not grouping cases properly