Nested conditional statements in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if a number is positive.

C++

#include <iostream>
int main() {
    int num = 5;
    if (num [1] 0) {
        std::cout << "Positive" << std::endl;
    }
    return 0;
}

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

A>

B!=

C==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' will check for negative numbers.

Using '==' checks for equality, not positivity.

The condition 'num > 0' checks if the number is positive.

2fill in blank

medium

Complete the code to check if a number is between 1 and 10 (inclusive).

C++

#include <iostream>
int main() {
    int num = 7;
    if (num [1] 1 && num [2] 10) {
        std::cout << "In range" << std::endl;
    }
    return 0;
}

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

A>=

B<=

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' or '<' excludes the boundary numbers.

Using '||' instead of '&&' allows numbers outside the range.

The condition 'num >= 1 && num <= 10' checks if num is between 1 and 10 inclusive.

3fill in blank

hard

Fix the error in the nested if statement to check if a number is positive and even.

C++

#include <iostream>
int main() {
    int num = 4;
    if (num > 0) {
        if (num [1] 2 == 0) {
            std::cout << "Positive and even" << std::endl;
        }
    }
    return 0;
}

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

A+

B/

C*

D%

Attempts:

3 left

💡 Hint

Common Mistakes

Using '/' divides the number but does not check evenness.

Using '*' or '+' are arithmetic operations unrelated to checking evenness.

The modulus operator '%' checks if the remainder is zero, meaning the number is even.

4fill in blank

hard

Fill both blanks to complete the nested conditional that prints if a number is positive and divisible by 3.

C++

#include <iostream>
int main() {
    int num = 9;
    if (num [1] 0) {
        if (num [2] 3 == 0) {
            std::cout << "Positive and divisible by 3" << std::endl;
        }
    }
    return 0;
}

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

A>

B<

C%

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' for positivity.

Using '/' instead of '%' for divisibility check.

The first condition checks if num is greater than 0, the second uses '%' to check divisibility by 3.

5fill in blank

hard

Fill all three blanks to create a nested conditional that prints if a number is negative, odd, and less than -10.

C++

#include <iostream>
int main() {
    int num = -15;
    if (num [1] 0) {
        if (num [2] 2 != 0) {
            if (num [3] -10) {
                std::cout << "Negative, odd, and less than -10" << std::endl;
            }
        }
    }
    return 0;
}

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

A<

B%

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '<' for negativity or less than -10.

Using '/' instead of '%' for oddness check.

The first condition checks if num is less than 0 (negative), the second uses '%' to check oddness, the third checks if num is less than -10.

Practice

1.

What does a nested conditional statement mean in C++?

easy

A. A loop inside a function

B. An if or else inside another if or else

C. A variable declared inside a function

D. A function calling itself

Solution

1. Step 1: Understand the meaning of nested conditionals

   Nested conditionals mean placing one if or else inside another to check multiple conditions step-by-step.

2. Step 2: Match the definition to the options

   An if or else inside another if or else correctly describes this as an if or else inside another if or else.

3. Final Answer:

   An if or else inside another if or else -> Option B

4. Quick Check:

   Nested conditional = if inside if [OK]

Hint: Look for condition inside another condition [OK]

Common Mistakes:

• Confusing nested conditionals with loops
• Thinking nested means multiple variables
• Mixing nested conditionals with recursion

2.

Which of the following is the correct syntax for a nested if statement in C++?

if (x > 0) {
    if (y < 10) {
        // code
    }
}

easy

A. if (x > 0) { if (y < 10) { // code } }

B. if (x > 0) if (y < 10) // code

C. if (x > 0) else if (y < 10) { // code }

D. if (x > 0) { else if (y < 10) { // code } }

Solution

1. Step 1: Check proper use of braces in nested if

   Correct nested if requires braces around inner if block inside outer if.

2. Step 2: Identify correct syntax option

   if (x > 0) { if (y < 10) { // code } } shows braces properly enclosing the inner if inside the outer if, which is correct syntax.

3. Final Answer:

   if (x > 0) { if (y < 10) { // code } } -> Option A

4. Quick Check:

   Braces around nested if blocks = correct syntax [OK]

Hint: Use braces {} to group nested if blocks [OK]

Common Mistakes:

• Missing braces causing syntax errors
• Using else if incorrectly inside nested if
• Placing else without matching if

3.

What is the output of the following C++ code?

int x = 5, y = 8;
if (x > 0) {
    if (y < 10) {
        std::cout << "A";
    } else {
        std::cout << "B";
    }
} else {
    std::cout << "C";
}

medium

A. No output

B. B

C. A

D. C

Solution

1. Step 1: Evaluate outer if condition

   Since x = 5 which is greater than 0, the outer if condition is true, so we enter the first block.

2. Step 2: Evaluate inner if condition

   Inside the outer block, y = 8 which is less than 10, so the inner if condition is true and prints "A".

3. Final Answer:

   A -> Option C

4. Quick Check:

   Both conditions true, print "A" [OK]

Hint: Check outer condition first, then inner [OK]

Common Mistakes:

• Ignoring inner condition and printing wrong letter
• Confusing else blocks
• Assuming else runs when outer if is true

4.

Find the error in this nested conditional code:

int a = 3;
if (a > 0)
    if (a < 5)
        std::cout << "Yes";
    else
        std::cout << "No";
else
    std::cout << "Maybe";

medium

A. Missing braces cause else to pair with wrong if

B. Syntax error: missing semicolon after if

C. Variable a is not declared

D. No error, code runs fine

Solution

1. Step 1: Analyze the indentation and else pairing

   Without braces, the else pairs with the nearest if, which can cause confusion in nested ifs.

2. Step 2: Identify the problem caused by missing braces

   Here, the else pairs with the inner if, not the outer, which may not be intended and causes logic errors.

3. Final Answer:

   Missing braces cause else to pair with wrong if -> Option A

4. Quick Check:

   Braces needed to avoid else ambiguity [OK]

Hint: Always use braces to avoid else ambiguity [OK]

Common Mistakes:

• Assuming else pairs with outer if
• Ignoring indentation does not affect pairing
• Thinking semicolon missing causes error

5.

Consider this 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";
    }
}

How can you rewrite this nested conditional using else if to improve clarity?

hard

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

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

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

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

Solution

1. Step 1: Understand nested if-else structure

   The original code uses an if inside an else to check score ranges.

2. Step 2: Rewrite using else if for clarity

   Using else if combines the conditions in a clear chain, avoiding deep nesting.

3. Final Answer:

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

4. Quick Check:

   Use else if to flatten nested conditionals [OK]

Hint: Use else if to avoid nested if inside else [OK]

Common Mistakes:

• Using multiple ifs without else causing multiple outputs
• Placing else without matching if
• Incorrect order of conditions