Switch statement - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of switch with fall-through

What is the output of this C code snippet?

C

#include <stdio.h>

int main() {
    int x = 2;
    switch (x) {
        case 1:
            printf("One\n");
        case 2:
            printf("Two\n");
        case 3:
            printf("Three\n");
            break;
        default:
            printf("Default\n");
    }
    return 0;
}

A

Two

B

One
Two
Three

C

Two
Three

D

Default

💡 Hint

Remember that cases fall through unless you use break.

Since x is 2, execution starts at case 2 and continues until a break is found. So it prints "Two" and "Three".

❓ Predict Output

intermediate

Value of variable after switch

What is the value of variable result after running this code?

C

#include <stdio.h>

int main() {
    int code = 3;
    int result = 0;
    switch (code) {
        case 1:
            result = 10;
            break;
        case 2:
            result = 20;
            break;
        case 3:
            result = 30;
        case 4:
            result += 5;
            break;
        default:
            result = -1;
    }
    printf("%d\n", result);
    return 0;
}

A 35

B 30

C -1

D 20

💡 Hint

Check if there is a break after case 3.

Since case 3 has no break, execution falls through to case 4, adding 5 to result (30 + 5 = 35).

❓ Predict Output

advanced

Output with multiple cases combined

What is the output of this program?

C

#include <stdio.h>

int main() {
    int day = 5;
    switch (day) {
        case 1:
        case 2:
        case 3:
            printf("Weekday\n");
            break;
        case 4:
        case 5:
            printf("Almost weekend\n");
            break;
        case 6:
        case 7:
            printf("Weekend\n");
            break;
        default:
            printf("Invalid day\n");
    }
    return 0;
}

A

Weekend

B

Almost weekend

C

Weekday

D

Invalid day

💡 Hint

Cases 4 and 5 share the same code block.

Since day is 5, it matches case 5, which prints "Almost weekend".

❓ Predict Output

advanced

Error caused by invalid switch expression type

What error will this code produce when compiled?

C

#include <stdio.h>

int main() {
    float value = 2.5;
    switch (value) {
        case 1.0:
            printf("One\n");
            break;
        case 2.5:
            printf("Two point five\n");
            break;
        default:
            printf("Default\n");
    }
    return 0;
}

A Compile error: switch expression must be an integer type

B Runtime error: invalid case label

C Output: Two point five

D Output: Default

💡 Hint

Check the type allowed in switch expressions in C.

In C, the switch expression must be an integer type. Using float causes a compile error.

🧠 Conceptual

expert

Number of times default executes in nested switches

Consider this nested switch code. How many times will the default case print "Default" when outer = 1 and inner = 3?

C

#include <stdio.h>

int main() {
    int outer = 1;
    int inner = 3;
    switch (outer) {
        case 1:
            switch (inner) {
                case 1:
                    printf("Inner One\n");
                    break;
                case 2:
                    printf("Inner Two\n");
                    break;
                default:
                    printf("Default\n");
            }
            break;
        default:
            printf("Default\n");
    }
    return 0;
}

A 3

B 2

C 0

D 1

💡 Hint

Check which switch executes default with given values.

The outer switch matches case 1, so it does not print default. The inner switch with inner=3 hits default once, printing "Default" once.

Practice

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

easy

A. To define a function

B. To repeat a block of code multiple times

C. To select one action from multiple choices based on a variable's value

D. To declare variables

Solution

1. Step 1: Understand the role of switch

   A switch statement chooses one path among many based on a variable's value.

2. Step 2: Compare with other options

   Loops repeat code, functions define reusable blocks, and declarations create variables, which are different from switch's purpose.

3. Final Answer:

   To select one action from multiple choices based on a variable's value -> Option C

4. Quick Check:

   Switch = Choice selection [OK]

Hint: Switch picks one case based on value, like a menu choice [OK]

Common Mistakes:

• Confusing switch with loops
• Thinking switch defines functions
• Believing switch declares variables

2. Which of the following is the correct syntax to start a switch statement in C?

easy

A. switch (variable) { case 1: ... }

B. switch variable { case 1: ... }

C. switch [variable] { case 1: ... }

D. switch variable: case 1: ...

Solution

1. Step 1: Recall switch syntax

   The correct syntax uses parentheses around the variable: switch(variable) { ... }

2. Step 2: Check options

   Only switch (variable) { case 1: ... } uses parentheses correctly; others miss parentheses or use wrong brackets.

3. Final Answer:

   switch (variable) { case 1: ... } -> Option A

4. Quick Check:

   Switch needs parentheses around variable [OK]

Hint: Remember: switch(variable) uses parentheses, not brackets or none [OK]

Common Mistakes:

• Omitting parentheses around variable
• Using square brackets instead of parentheses
• Using colon instead of braces

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

int x = 2;
switch (x) {
  case 1:
    printf("One\n");
    break;
  case 2:
    printf("Two\n");
    break;
  default:
    printf("Other\n");
}

medium

A. One

B. Other

C. No output

D. Two

Solution

1. Step 1: Identify the switch variable value

   The variable x is 2, so the switch checks case 2.

2. Step 2: Match case and output

   Case 2 matches, so it prints "Two" and then breaks to stop further checks.

3. Final Answer:

   Two -> Option D

4. Quick Check:

   Case 2 matches x=2, prints "Two" [OK]

Hint: Match variable value to case, print and break [OK]

Common Mistakes:

• Forgetting break causes fall-through
• Choosing default when case matches
• Confusing case numbers

4. Find the error in this switch statement:

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

medium

A. Missing break after case 1

B. Missing default case

C. Wrong switch syntax

D. Variable n not declared

Solution

1. Step 1: Check each case for break

   Case 1 lacks a break, so if matched, it would fall through to case 2.

2. Step 2: Understand impact

   Missing break can cause unintended multiple prints; adding break after case 1 fixes this.

3. Final Answer:

   Missing break after case 1 -> Option A

4. Quick Check:

   Each case needs break to stop fall-through [OK]

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

Common Mistakes:

• Ignoring missing break causes fall-through
• Thinking default is mandatory
• Assuming variable declaration error

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 correctly does this?

hard

A. switch(day) { case 1: printf("Weekday\n"); break; case 2: printf("Weekday\n"); break; case 3: printf("Weekend\n"); break; case 4: printf("Weekday\n"); break; case 5: printf("Weekday\n"); break; case 6: printf("Weekend\n"); break; case 7: printf("Weekend\n"); break; }

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

C. switch(day) { case 1: case 2: case 3: case 4: case 5: printf("Weekend\n"); break; case 6: case 7: printf("Weekday\n"); break; }

D. switch(day) { case 1: case 2: case 3: case 4: case 5: printf("Weekday\n"); case 6: case 7: printf("Weekend\n"); break; }

Solution

1. Step 1: Group cases for same output

   Cases 1 to 5 print "Weekday", so group them before one printf and break.

2. Step 2: Group weekend cases

   Cases 6 and 7 print "Weekend" similarly grouped with break.

3. Step 3: Check default case

   switch(day) { case 1: case 2: case 3: case 4: case 5: printf("Weekday\n"); break; case 6: case 7: printf("Weekend\n"); break; default: printf("Invalid\n"); } includes default for invalid days, which is good practice.

4. Final Answer:

   Groups weekday cases 1-5 and weekend cases 6-7 with breaks and default -> Option B

5. Quick Check:

   Group cases with same output, add break after each group [OK]

Hint: Group cases with same output, add break after group [OK]

Common Mistakes:

• Printing wrong labels for grouped cases
• Missing breaks causing fall-through
• Not handling default case