Else–if ladder in C - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of an else-if ladder with multiple conditions

What is the output of the following C code?

C

#include <stdio.h>

int main() {
    int x = 15;
    if (x < 10) {
        printf("Less than 10\n");
    } else if (x < 20) {
        printf("Between 10 and 19\n");
    } else if (x < 30) {
        printf("Between 20 and 29\n");
    } else {
        printf("30 or more\n");
    }
    return 0;
}

A Less than 10

B Between 20 and 29

C Between 10 and 19

D 30 or more

💡 Hint

Check which condition matches first in the else-if ladder.

The variable x is 15, which is not less than 10, so the first if fails. The second condition checks if x < 20, which is true, so it prints "Between 10 and 19" and skips the rest.

❓ Predict Output

intermediate

Output when all else-if conditions fail

What will this C program print?

C

#include <stdio.h>

int main() {
    int num = 50;
    if (num < 10) {
        printf("Small number\n");
    } else if (num < 20) {
        printf("Medium number\n");
    } else if (num < 30) {
        printf("Large number\n");
    } else {
        printf("Extra large number\n");
    }
    return 0;
}

A Extra large number

B Medium number

C Large number

D Small number

💡 Hint

Check which condition matches the value 50.

The value 50 does not satisfy any of the first three conditions, so the else block runs and prints "Extra large number".

🔧 Debug

advanced

Identify the error in else-if ladder syntax

What error does this C code produce when compiled?

C

#include <stdio.h>

int main() {
    int a = 5;
    if (a > 0) {
        printf("Positive\n");
    } else if a == 0 {
        printf("Zero\n");
    } else {
        printf("Negative\n");
    }
    return 0;
}

A Runtime error: segmentation fault

B TypeError: invalid comparison

C No error, prints 'Zero'

D SyntaxError: missing parentheses in else-if condition

💡 Hint

Check the syntax of the else-if condition.

In C, the condition in else-if must be enclosed in parentheses. The code 'else if a == 0' is missing parentheses, causing a syntax error.

❓ Predict Output

advanced

Output of nested else-if ladder with multiple variables

What is the output of this C program?

C

#include <stdio.h>

int main() {
    int x = 8, y = 12;
    if (x > 10) {
        if (y > 10) {
            printf("x > 10 and y > 10\n");
        } else {
            printf("x > 10 and y <= 10\n");
        }
    } else if (x > 5) {
        printf("x between 6 and 10\n");
    } else {
        printf("x 5 or less\n");
    }
    return 0;
}

A x > 10 and y > 10

B x between 6 and 10

C x > 10 and y <= 10

D x 5 or less

💡 Hint

Check the first condition and then the else-if condition carefully.

x is 8, which is not greater than 10, so the first if block is skipped. The else-if checks if x > 5, which is true, so it prints "x between 6 and 10".

🧠 Conceptual

expert

Number of times conditions are evaluated in else-if ladder

Consider this else-if ladder in C:

if (cond1) {
    // block1
} else if (cond2) {
    // block2
} else if (cond3) {
    // block3
} else {
    // block4
}

If cond1 is false, cond2 is true, and cond3 is true, how many conditions are evaluated before executing a block?

A 2 conditions

B 1 condition

C 3 conditions

D 4 conditions

💡 Hint

Remember else-if stops checking after the first true condition.

The program checks cond1 (false), then cond2 (true). Since cond2 is true, it executes block2 and stops. So only 2 conditions are evaluated.

Practice

1. What does an else-if ladder do in C programming?

easy

A. Checks multiple conditions one by one and executes the first true block

B. Runs all conditions regardless of their truth value

C. Only executes the last condition in the ladder

D. Skips all conditions and runs the else block always

Solution

1. Step 1: Understand the purpose of else-if ladder

   An else-if ladder is used to check multiple conditions sequentially.

2. Step 2: Identify how conditions are executed

   Only the first condition that is true will have its block executed, and the rest are skipped.

3. Final Answer:

   Checks multiple conditions one by one and executes the first true block -> Option A

4. Quick Check:

   Else-if ladder = first true condition runs [OK]

Hint: Remember: else-if stops at first true condition [OK]

Common Mistakes:

• Thinking all conditions run regardless
• Believing else runs always
• Confusing else-if with multiple ifs

2. Which of the following is the correct syntax for an else-if ladder in C?

easy

A. if(condition) { } else(condition) { } else if { }

B. if(condition) { } else if(condition) { } else { }

C. if(condition) { } else if { } else(condition) { }

D. if(condition) { } else if(condition) { } else if

Solution

1. Step 1: Review correct else-if syntax

   The else-if ladder uses: if(condition) { } else if(condition) { } else { }.

2. Step 2: Check each option for syntax errors

   if(condition) { } else if(condition) { } else { } matches correct syntax; others have misplaced else or missing conditions.

3. Final Answer:

   if(condition) { } else if(condition) { } else { } -> Option B

4. Quick Check:

   Correct else-if syntax = if(condition) { } else if(condition) { } else { } [OK]

Hint: else if always needs a condition in parentheses [OK]

Common Mistakes:

• Writing else with a condition
• Omitting parentheses in else-if
• Ending else-if without braces

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

int x = 15;
if (x < 10) {
  printf("Less than 10\n");
} else if (x < 20) {
  printf("Less than 20\n");
} else {
  printf("20 or more\n");
}

medium

A. Less than 20

B. 20 or more

C. Less than 10

D. No output

Solution

1. Step 1: Evaluate first condition (x < 10)

   x is 15, which is not less than 10, so this block is skipped.

2. Step 2: Evaluate second condition (x < 20)

   15 is less than 20, so this block runs and prints "Less than 20".

3. Final Answer:

   Less than 20 -> Option A

4. Quick Check:

   15 < 20 = true, prints "Less than 20" [OK]

Hint: Check conditions top to bottom, first true runs [OK]

Common Mistakes:

• Choosing first condition without checking value
• Assuming else always runs
• Confusing output strings

4. Find the error in this else-if ladder code snippet:

int num = 5;
if (num > 10)
  printf("Greater than 10\n");
else if num > 0
  printf("Positive number\n");
else
  printf("Zero or negative\n");

medium

A. Missing semicolon after printf statements

B. else cannot be used without if

C. Incorrect variable name used

D. Missing parentheses around condition in else-if

Solution

1. Step 1: Check syntax of else-if condition

   In C, else-if condition must be inside parentheses: else if (condition).

2. Step 2: Identify the error in given code

   Code has else if num > 0 without parentheses, causing syntax error.

3. Final Answer:

   Missing parentheses around condition in else-if -> Option D

4. Quick Check:

   else-if needs parentheses [OK]

Hint: Always put conditions in parentheses after else if [OK]

Common Mistakes:

• Forgetting parentheses in else-if
• Missing semicolons after printf
• Misusing else without if

5. You want to write a program that prints "Child" if age < 13, "Teen" if age is between 13 and 19 inclusive, "Adult" if age is between 20 and 59 inclusive, and "Senior" if age is 60 or more. Which else-if ladder correctly implements this?

hard

A. if (age < 13) { printf("Child\n"); } else if (age < 20) { printf("Teen\n"); } else if (age < 59) { printf("Adult\n"); } else { printf("Senior\n"); }

B. if (age <= 13) { printf("Child\n"); } else if (age < 19) { printf("Teen\n"); } else if (age < 59) { printf("Adult\n"); } else { printf("Senior\n"); }

C. if (age <= 12) { printf("Child\n"); } else if (age <= 19) { printf("Teen\n"); } else if (age <= 59) { printf("Adult\n"); } else { printf("Senior\n"); }

D. if (age < 13) { printf("Child\n"); } else if (age < 19) { printf("Teen\n"); } else if (age <= 59) { printf("Adult\n"); } else { printf("Senior\n"); }

Solution

1. Step 1: Analyze age ranges for each category

   Child: age < 13 means age ≤ 12; Teen: 13 to 19 inclusive; Adult: 20 to 59 inclusive; Senior: 60 or more.

2. Step 2: Check each option's conditions

   if (age <= 12) { printf("Child\n"); } else if (age <= 19) { printf("Teen\n"); } else if (age <= 59) { printf("Adult\n"); } else { printf("Senior\n"); } correctly uses age ≤ 12 for Child, ≤ 19 for Teen, ≤ 59 for Adult, else Senior.

3. Final Answer:

   if (age <= 12) { printf("Child\n"); } else if (age <= 19) { printf("Teen\n"); } else if (age <= 59) { printf("Adult\n"); } else { printf("Senior\n"); } -> Option C

4. Quick Check:

   Correct age ranges with inclusive bounds = if (age <= 12) { printf("Child\n"); } else if (age <= 19) { printf("Teen\n"); } else if (age <= 59) { printf("Adult\n"); } else { printf("Senior\n"); } [OK]

Hint: Use inclusive bounds carefully in else-if conditions [OK]

Common Mistakes:

• Using wrong comparison operators
• Overlapping or missing age ranges
• Incorrect boundary values