Switch vs if comparison in C++ - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print "One" when the variable num is 1.

C++

int num = 1;
switch (num) {
    case [1]:
        std::cout << "One" << std::endl;
        break;
    default:
        std::cout << "Other" << std::endl;
}

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

A1

B2

C0

Ddefault

Attempts:

3 left

💡 Hint

Common Mistakes

Using a case label that does not match the variable value.

Using 'default' as a case label.

The case label must match the value of num to execute the correct block. Here, case 1: matches num = 1.

2fill in blank

medium

Complete the if statement to print "Two" when num equals 2.

C++

int num = 2;
if (num [1] 2) {
    std::cout << "Two" << std::endl;
} else {
    std::cout << "Not Two" << std::endl;
}

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

A!=

B<

C>

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using assignment operator '=' instead of comparison '=='.

Using inequality operator '!='.

The equality operator == checks if num is equal to 2.

3fill in blank

hard

Fix the error in the switch statement to correctly handle the variable grade.

C++

char grade = 'B';
switch (grade) {
    case [1]:
        std::cout << "Good" << std::endl;
        break;
    default:
        std::cout << "Other grade" << std::endl;
}

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

A"B"

B'B'

CB

D"b"

Attempts:

3 left

💡 Hint

Common Mistakes

Using double quotes instead of single quotes for characters.

Using unquoted letters.

Character constants in C++ use single quotes. Double quotes are for strings.

4fill in blank

hard

Fill both blanks to create a map from numbers to words using if statements.

C++

int num = 3;
if (num [1] 1) {
    std::cout << "One" << std::endl;
} else if (num [2] 3) {
    std::cout << "Three" << std::endl;
} else {
    std::cout << "Other" << std::endl;
}

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

A==

B!=

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using inequality operator '!=' instead of '=='.

Using greater or less than operators incorrectly.

Use the equality operator == to check if num equals 1 or 3.

5fill in blank

hard

Fill all three blanks to create a switch statement that prints the day of the week for 1, 2, and 3.

C++

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

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

A1

B2

C3

D4

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong numbers for case labels.

Missing break statements (though not asked here).

The case labels must match the values 1, 2, and 3 to print the correct day.

Practice

1. Which statement best describes when to use switch instead of if in C++?

easy

A. switch can handle complex conditions like ranges.

B. if cannot be used with multiple conditions.

C. if is only for checking equality.

D. switch is best for many fixed, discrete values.

Solution

1. Step 1: Understand switch usage

   switch works well when you have many fixed values to compare, like numbers or characters.

2. Step 2: Compare with if

   if can handle any condition, including ranges or complex logic, but switch is simpler for fixed choices.

3. Final Answer:

   switch is best for many fixed, discrete values. -> Option D

4. Quick Check:

   Use switch for fixed values = B [OK]

Hint: Use switch for fixed values, if for complex conditions [OK]

Common Mistakes:

• Thinking switch can handle ranges
• Believing if is only for equality
• Assuming if cannot handle multiple conditions

2. Which of the following is the correct syntax for a switch statement in C++?

easy

A. switch variable { case 1: doSomething(); break; default: doDefault(); }

B. switch (variable) { case 1: doSomething(); break; default: doDefault(); }

C. switch (variable) do { case 1: doSomething(); break; }

D. switch (variable) { if case 1: doSomething(); }

Solution

1. Step 1: Recall correct switch syntax

   The switch statement requires parentheses around the variable and curly braces enclosing cases.

2. Step 2: Check each option

   switch (variable) { case 1: doSomething(); break; default: doDefault(); } uses correct syntax with parentheses, cases, and breaks. Others miss parentheses, use wrong keywords, or incorrect structure.

3. Final Answer:

   switch (variable) { case 1: doSomething(); break; default: doDefault(); } -> Option B

4. Quick Check:

   Parentheses and braces needed in switch = A [OK]

Hint: Remember switch(variable) with braces and cases [OK]

Common Mistakes:

• Omitting parentheses around variable
• Using 'if' inside switch incorrectly
• Missing curly braces for cases

3. What will be the output of this C++ code?

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

medium

A. TwoThree

B. Two

C. Three

D. Other

Solution

1. Step 1: Identify matching case

   The variable x is 2, so the switch jumps to case 2.

2. Step 2: Trace output and breaks

   It prints "Two" but no break after case 2, so it continues to case 3 and prints "Three" before breaking.

3. Final Answer:

   TwoThree -> Option A

4. Quick Check:

   Missing break causes fall-through = TwoThree [OK]

Hint: Remember missing break causes fall-through in switch [OK]

Common Mistakes:

• Assuming only case 2 prints
• Forgetting fall-through behavior
• Confusing default case execution

4. Identify the error in this code snippet:

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. Switch variable must be a string.

C. Missing break after case 1 causes fall-through.

D. Case labels must be in ascending order.

Solution

1. Step 1: Check switch cases and breaks

   Case 1 lacks a break, so if n == 1, it will fall through to case 2 and print both outputs.

2. Step 2: Verify other rules

   Switch variable can be int, default can be anywhere, and case order does not matter.

3. Final Answer:

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

4. Quick Check:

   Break needed to prevent fall-through = A [OK]

Hint: Always add break after each case unless fall-through wanted [OK]

Common Mistakes:

• Thinking switch variable must be string
• Believing default must be last
• Assuming case order matters

5. You want to check if an integer variable score is between 90 and 100 (inclusive) to print "Excellent", between 75 and 89 to print "Good", and otherwise print "Try again". Which approach is better and why?

hard

A. Use if because switch cannot handle ranges.

B. Use if only for equality checks.

C. Use switch with multiple cases for each number in the range.

D. Use switch because it is simpler for ranges.

Solution

1. Step 1: Understand the problem with ranges

   The conditions check if score falls within ranges, not fixed values.

2. Step 2: Compare switch and if suitability

   switch cannot directly handle ranges; if can use relational operators to check ranges easily.

3. Final Answer:

   Use if because switch cannot handle ranges. -> Option A

4. Quick Check:

   Ranges need if, not switch = D [OK]

Hint: Use if for ranges, switch only for fixed values [OK]

Common Mistakes:

• Trying to use switch for ranges
• Using switch with many case labels for ranges
• Thinking if only checks equality