Nested conditional execution in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested if-else with integer input

What is the output of the following C# code?

C Sharp (C#)

int x = 7;
if (x > 5)
{
    if (x < 10)
    {
        Console.WriteLine("A");
    }
    else
    {
        Console.WriteLine("B");
    }
}
else
{
    Console.WriteLine("C");
}

A No output

B B

C A

D C

💡 Hint

Check the conditions step by step starting from the outer if.

The variable x is 7, which is greater than 5, so the outer if is true. Then the inner if checks if x is less than 10, which is also true. So it prints "A".

❓ Predict Output

intermediate

Nested if-else with string comparison

What will be printed when this code runs?

C Sharp (C#)

string color = "red";
if (color == "blue")
{
    Console.WriteLine("Blue selected");
}
else
{
    if (color == "red")
    {
        Console.WriteLine("Red selected");
    }
    else
    {
        Console.WriteLine("Other color");
    }
}

A Red selected

B Blue selected

C Other color

D No output

💡 Hint

Check the value of the variable and the conditions carefully.

The variable color is "red", so the first if condition is false. The else block runs, and inside it the inner if checks if color is "red", which is true, so it prints "Red selected".

🔧 Debug

advanced

Identify the error in nested if-else code

What error will this C# code produce when compiled?

C Sharp (C#)

int n = 3;
if (n > 0)
    if (n < 5)
        Console.WriteLine("In range");
    else
        Console.WriteLine("Out of range");
else
    Console.WriteLine("Negative");
else
    Console.WriteLine("Zero");

A No error, prints "In range"

B Syntax error: else without matching if

C Runtime error: ambiguous else

D Syntax error: missing braces

💡 Hint

Look carefully at the placement of else statements and braces.

The code has two else statements at the same indentation level but only one if to match. This causes a syntax error: 'else' without a matching 'if'.

🚀 Application

advanced

Determine output of nested if with multiple conditions

What is the output of this code snippet?

C Sharp (C#)

int score = 85;
if (score >= 90)
{
    Console.WriteLine("Grade A");
}
else
{
    if (score >= 80)
    {
        Console.WriteLine("Grade B");
    }
    else
    {
        Console.WriteLine("Grade C");
    }
}

A Grade A

B No output

C Grade C

D Grade B

💡 Hint

Check the score against each condition carefully.

The score is 85, which is not >= 90, so the first if is false. The else block runs, and inside it the inner if checks if score >= 80, which is true, so it prints "Grade B".

🧠 Conceptual

expert

Understanding nested if-else flow

Consider this nested if-else structure:

if (A)
{
    if (B)
    {
        Action1;
    }
    else
    {
        Action2;
    }
}
else
{
    Action3;
}

Which statement is true about when Action2 executes?

A When A is true and B is false

B When A is false and B is true

C When A is false and B is false

D When B is true regardless of A

💡 Hint

Trace the conditions that lead to the else inside the first if.

Action2 is inside the else of the inner if (B). It runs only if A is true (outer if) and B is false (inner else).

Practice

1. What does nested conditional execution mean in C#?

easy

A. Running code without any conditions

B. Checking one condition inside another condition

C. Using only one if statement without else

D. Writing multiple if statements separately

Solution

1. Step 1: Understand the meaning of nested conditions

   Nested conditional execution means putting one if or else if statement inside another to check multiple conditions step-by-step.

2. Step 2: Compare options with definition

   Only Checking one condition inside another condition describes checking one condition inside another, which matches nested conditional execution.

3. Final Answer:

   Checking one condition inside another condition -> Option B

4. Quick Check:

   Nested condition = condition inside condition [OK]

Hint: Think of conditions inside conditions like boxes inside boxes [OK]

Common Mistakes:

• Confusing nested with multiple separate if statements
• Thinking nested means no else parts
• Believing nested means no conditions at all

2. Which of the following is the correct syntax for nested if statements in C#?

easy

A. if (x > 0) { if (x < 10) { Console.WriteLine("Inside"); } }

B. if x > 0 then if x < 10 then Console.WriteLine("Inside")

C. if (x > 0 if (x < 10) Console.WriteLine("Inside") else Console.WriteLine("Outside");

D. if (x > 0) { Console.WriteLine("Inside"); } else if (x < 10) { Console.WriteLine("Inside"); }

Solution

1. Step 1: Review C# nested if syntax

   Nested if means an if statement inside another if's braces, both with parentheses and braces.

2. Step 2: Check each option

   if (x > 0) { if (x < 10) { Console.WriteLine("Inside"); } } correctly uses braces and parentheses for nested if. if x > 0 then if x < 10 then Console.WriteLine("Inside") uses wrong syntax (no parentheses). if (x > 0 if (x < 10) Console.WriteLine("Inside") else Console.WriteLine("Outside"); misses braces and has syntax error (missing closing parenthesis). if (x > 0) { Console.WriteLine("Inside"); } else if (x < 10) { Console.WriteLine("Inside"); } is separate if-else, not nested.

3. Final Answer:

   if (x > 0) { if (x < 10) { Console.WriteLine("Inside"); } } -> Option A

4. Quick Check:

   Nested if needs braces and parentheses [OK]

Hint: Look for braces inside braces with proper parentheses [OK]

Common Mistakes:

• Omitting parentheses around conditions
• Missing braces for nested blocks
• Confusing else placement in nested if

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

int x = 5;
if (x > 0) {
  if (x < 10) {
    Console.WriteLine("A");
  } else {
    Console.WriteLine("B");
  }
} else {
  Console.WriteLine("C");
}

medium

A. A

B. B

C. C

D. No output

Solution

1. Step 1: Check outer if condition

   x = 5, so x > 0 is true, enter first if block.

2. Step 2: Check inner if condition

   Inside first if, check if x < 10. Since 5 < 10 is true, print "A".

3. Final Answer:

   A -> Option A

4. Quick Check:

   x=5 >0 and <10 prints A [OK]

Hint: Follow conditions step-by-step inside each if [OK]

Common Mistakes:

• Ignoring inner if and printing else block
• Confusing else belonging to which if
• Assuming no output if conditions are true

4. Find the error in this nested conditional code:

int y = 8;
if (y > 5)
  if (y < 10)
    Console.WriteLine("Inside");
  else
    Console.WriteLine("Outside");

medium

A. Missing braces causing else to pair with wrong if

B. Syntax error: missing semicolon after if

C. Variable y is not declared

D. No error, code runs fine

Solution

1. Step 1: Analyze if-else pairing without braces

   Without braces, else pairs with nearest if (the inner one). This is correct C# syntax.

2. Step 2: Check for errors

   The code compiles and runs fine with no syntax error, undefined variables, or crashes. Braces are recommended for clarity but not required here.

3. Final Answer:

   No error, code runs fine -> Option D

4. Quick Check:

   Code runs correctly without braces [OK]

Hint: Use braces to clearly group if-else blocks [OK]

Common Mistakes:

• Thinking semicolon needed after if
• Assuming else pairs with outer if
• Ignoring braces importance

5. You want to write a nested conditional in C# that prints "Small Positive" if a number is greater than 0 and less than 10, "Large Positive" if greater or equal to 10, and "Non-positive" otherwise. Which code correctly implements this?

hard

A. if (num < 10) { if (num > 0) { Console.WriteLine("Non-positive"); } else { Console.WriteLine("Small Positive"); } } else { Console.WriteLine("Large Positive"); }

B. if (num > 0 && num < 10) { Console.WriteLine("Small Positive"); } else if (num >= 10) { Console.WriteLine("Large Positive"); } else { Console.WriteLine("Non-positive"); }

C. if (num > 0) { if (num < 10) { Console.WriteLine("Small Positive"); } else { Console.WriteLine("Large Positive"); } } else { Console.WriteLine("Non-positive"); }

D. if (num > 0) { Console.WriteLine("Small Positive"); } else if (num < 10) { Console.WriteLine("Large Positive"); } else { Console.WriteLine("Non-positive"); }

Solution

1. Step 1: Understand conditions to check

   We want to check if num > 0 and num < 10 for "Small Positive", else if num >= 10 for "Large Positive", else "Non-positive".

2. Step 2: Check nested if logic

   if (num > 0) { if (num < 10) { Console.WriteLine("Small Positive"); } else { Console.WriteLine("Large Positive"); } } else { Console.WriteLine("Non-positive"); } correctly nests the second condition inside the first if (num > 0), checking num < 10 inside it, else prints "Large Positive". Else prints "Non-positive".

3. Final Answer:

   if (num > 0) { if (num < 10) { Console.WriteLine("Small Positive"); } else { Console.WriteLine("Large Positive"); } } else { Console.WriteLine("Non-positive"); } -> Option C

4. Quick Check:

   Nested if matches conditions exactly [OK]

Hint: Nest second condition inside first to separate ranges clearly [OK]

Common Mistakes:

• Using && instead of nested if for this logic
• Swapping else blocks incorrectly
• Not covering all cases properly