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

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of an else-if ladder with integer input

What is the output of the following C++ code when num = 15?

C++

#include <iostream>
using namespace std;

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

A Between 10 and 19

B Less than 10

C Between 20 and 29

D 30 or more

💡 Hint

Check which condition is true first in the else-if ladder.

The variable num is 15. The first condition (num < 10) is false. The second condition (num < 20) is true, so it prints "Between 10 and 19" and skips the rest.

❓ Predict Output

intermediate

Output when multiple else-if conditions are false

What will the program print when score = 85 in this else-if ladder?

C++

#include <iostream>
using namespace std;

int main() {
    int score = 85;
    if (score >= 90) {
        cout << "Grade A";
    } else if (score >= 80) {
        cout << "Grade B";
    } else if (score >= 70) {
        cout << "Grade C";
    } else {
        cout << "Fail";
    }
    return 0;
}

A Grade A

B Grade B

C Grade C

D Fail

💡 Hint

Check the conditions from top to bottom carefully.

score is 85. The first condition (score >= 90) is false. The second condition (score >= 80) is true, so it prints "Grade B".

🔧 Debug

advanced

Identify the error in this else-if ladder

What error will this code produce when compiled?

C++

#include <iostream>
using namespace std;

int main() {
    int x = 5;
    if (x > 0)
        cout << "Positive";
    else if x == 0 {
        cout << "Zero";
    } else {
        cout << "Negative";
    }
    return 0;
}

A Logical error, prints wrong output

B Runtime error due to uninitialized variable

C No error, prints "Positive"

D Syntax error due to missing parentheses in else if condition

💡 Hint

Check the syntax of the else-if statement carefully.

In C++, the condition in else if must be enclosed in parentheses. The code has else if x == 0 without parentheses, causing a syntax error.

🧠 Conceptual

advanced

Understanding else-if ladder flow

Consider this else-if ladder. Which statement is true about how it executes?

C++

if (a > b) {
    // block 1
} else if (a == b) {
    // block 2
} else {
    // block 3
}

A All blocks can execute if conditions are true

B Blocks 1 and 3 can execute together

C Only one block executes depending on the first true condition

D Blocks 2 and 3 always execute together

💡 Hint

Think about how else-if ladder chooses which block to run.

In an else-if ladder, only the first true condition's block runs. The rest are skipped.

❓ Predict Output

expert

Output of nested else-if ladder with multiple variables

What is the output of this C++ program?

C++

#include <iostream>
using namespace std;

int main() {
    int x = 10, y = 20;
    if (x > y) {
        cout << "X is greater";
    } else if (x == y) {
        cout << "X equals Y";
    } else if (y - x == 10) {
        cout << "Difference is 10";
    } else {
        cout << "Other case";
    }
    return 0;
}

A Difference is 10

B X equals Y

C X is greater

D Other case

💡 Hint

Check each condition carefully in order.

x=10, y=20. First condition (x > y) is false. Second (x == y) is false. Third (y - x == 10) is true, so it prints "Difference is 10".

Practice

1.

What does an else-if ladder do in C++?

easy

A. Skips all conditions and runs the else block always

B. Runs all conditions regardless of their truth

C. Only runs the last condition in the ladder

D. Checks multiple conditions one by one and runs the first true block

Solution

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

   An else-if ladder is used to check multiple conditions in order, one after another.

2. Step 2: Identify how conditions are evaluated

   It runs the code block for the first condition that is true and skips the rest.

3. Final Answer:

   Checks multiple conditions one by one and runs the first true block -> Option D

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
• Believing else always runs
• Confusing else-if with separate ifs

2.

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

int x = 10;
if (x < 5) {
  // code A
} _____ (x < 15) {
  // code B
} else {
  // code C
}

easy

A. else if

B. elseif

C. else_if

D. else if()

Solution

1. Step 1: Recall correct else-if syntax in C++

   The correct keyword is else if with a space, no underscores or parentheses after else.

2. Step 2: Check each option

   Options A, B, and C are invalid syntax in C++.

3. Final Answer:

   else if -> Option A

4. Quick Check:

   Correct syntax = else if [OK]

Hint: Use 'else if' with space, no underscores or parentheses [OK]

Common Mistakes:

• Writing 'elseif' as one word
• Using underscores like 'else_if'
• Adding parentheses after else

3.

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

int num = 7;
if (num > 10) {
  std::cout << "Greater than 10";
} else if (num > 5) {
  std::cout << "Greater than 5";
} else {
  std::cout << "5 or less";
}

medium

A. Greater than 5

B. 5 or less

C. Greater than 10

D. No output

Solution

1. Step 1: Evaluate first condition (num > 10)

   7 is not greater than 10, so this block is skipped.

2. Step 2: Evaluate second condition (num > 5)

   7 is greater than 5, so this block runs and prints "Greater than 5".

3. Final Answer:

   Greater than 5 -> Option A

4. Quick Check:

   7 > 5 = true, prints "Greater than 5" [OK]

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

Common Mistakes:

• Choosing first condition output incorrectly
• Ignoring else-if order
• Assuming else runs always

4.

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

int score = 85;
if (score >= 90) {
  std::cout << "Grade A";
} else if score >= 80 {
  std::cout << "Grade B";
} else {
  std::cout << "Grade C";
}

medium

A. Missing semicolon after std::cout

B. Missing parentheses around condition in else-if

C. Incorrect use of else instead of else-if

D. Using >= instead of >

Solution

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

   In C++, conditions must be inside parentheses. The else-if line lacks parentheses.

2. Step 2: Verify other parts

   Semicolons and operators are correct; only parentheses are missing.

3. Final Answer:

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

4. Quick Check:

   Conditions need parentheses [OK]

Hint: Always put conditions inside parentheses [OK]

Common Mistakes:

• Forgetting parentheses in if/else-if
• Missing semicolons after statements
• Confusing else and else-if syntax

5.

Write an else-if ladder to print the day of the week given an integer day (1 to 7). What will be printed if day = 5?

int day = 5;
if (day == 1) {
  std::cout << "Monday";
} else if (day == 2) {
  std::cout << "Tuesday";
} else if (day == 3) {
  std::cout << "Wednesday";
} else if (day == 4) {
  std::cout << "Thursday";
} else if (day == 5) {
  std::cout << "Friday";
} else if (day == 6) {
  std::cout << "Saturday";
} else if (day == 7) {
  std::cout << "Sunday";
} else {
  std::cout << "Invalid day";
}

hard

A. Thursday

B. Saturday

C. Friday

D. Invalid day

Solution

1. Step 1: Match the value of day with conditions

   day is 5, so the else-if condition day == 5 is true.

2. Step 2: Identify the output for day == 5

   The code prints "Friday" for day 5.

3. Final Answer:

   Friday -> Option C

4. Quick Check:

   day 5 = Friday [OK]

Hint: Match day number to correct else-if condition [OK]

Common Mistakes:

• Mixing up day numbers and names
• Forgetting else block for invalid days
• Using wrong comparison operators