Ternary operator in C - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the ternary operator in C?

The ternary operator is a shorthand way to write an if-else statement. It uses the syntax: condition ? expression_if_true : expression_if_false;

beginner

How does the ternary operator work in C?

It evaluates the condition first. If the condition is true, it returns the first expression; if false, it returns the second expression.

beginner

Rewrite this if-else using the ternary operator:

if (a > b) {
  max = a;
} else {
  max = b;
}

Using ternary operator:

max = (a > b) ? a : b;

intermediate

Can the ternary operator be nested in C?

Yes, you can nest ternary operators inside each other, but it can make code harder to read. Example:

result = (a > b) ? a : ((b > c) ? b : c);

beginner

What is a common use case for the ternary operator?

It is often used for simple conditional assignments or returning values in a concise way instead of writing full if-else blocks.

What does the ternary operator syntax look like in C?

A expr1 ? condition : expr2

B if (condition) expr1 else expr2

C condition ? expr1, expr2

D condition ? expr1 : expr2

The ternary operator uses the syntax: condition ? expression_if_true : expression_if_false.

What value does the ternary operator return if the condition is false?

A The first expression

B The condition itself

C The second expression

D It returns nothing

If the condition is false, the ternary operator returns the second expression after the colon.

Which of these is a correct use of the ternary operator?

A max = if (a > b) a else b;

B max = (a > b) ? a : b;

C max = (a > b) : a ? b;

D max = a > b ? : b;

Option B correctly uses the ternary operator syntax.

Is it recommended to use nested ternary operators?

A Yes, but they can reduce readability

B No, they are not allowed

C Yes, always for clarity

D No, they cause syntax errors

Nested ternary operators are allowed but can make code harder to read.

What is a benefit of using the ternary operator?

A It simplifies simple conditional assignments

B It replaces loops

C It is slower than if-else

D It makes code longer

The ternary operator simplifies writing simple conditional assignments in a concise way.

Explain how the ternary operator works and write a simple example in C.

Think of it as a short if-else that returns a value.

Describe when you might prefer using the ternary operator instead of a full if-else statement.

Use it when you want to assign a value quickly based on a condition.

Practice

1. What does the ternary operator condition ? value_if_true : value_if_false do in C?

easy

A. It chooses one of two values based on the condition's truth.

B. It creates a loop that runs twice.

C. It declares a new variable.

D. It comments out code.

Solution

1. Step 1: Understand the ternary operator structure

   The ternary operator uses a condition followed by a question mark, then two values separated by a colon.

2. Step 2: Determine its purpose

   It returns the first value if the condition is true, otherwise the second value.

3. Final Answer:

   It chooses one of two values based on the condition's truth. -> Option A

4. Quick Check:

   condition ? true_value : false_value = chooses value [OK]

Hint: Remember: condition ? true : false picks one value [OK]

Common Mistakes:

• Thinking it creates loops
• Confusing it with variable declaration
• Assuming it comments code

2. Which of the following is the correct syntax for the ternary operator in C?

easy

A. condition : value_if_true ? value_if_false;

B. condition ? value_if_true : value_if_false;

C. condition ? value_if_true, value_if_false;

D. condition ? (value_if_true : value_if_false);

Solution

1. Step 1: Recall ternary operator syntax

   The correct syntax is: condition ? value_if_true : value_if_false;

2. Step 2: Check each option

   condition ? value_if_true : value_if_false; matches the correct syntax exactly; others have misplaced symbols or punctuation.

3. Final Answer:

   condition ? value_if_true : value_if_false; -> Option B

4. Quick Check:

   Syntax is condition ? true : false; [OK]

Hint: Remember: question mark before colon in ternary [OK]

Common Mistakes:

• Swapping question mark and colon
• Using comma instead of colon
• Adding extra parentheses incorrectly

3. What is the output of this C code?

int x = 5;
int y = (x > 3) ? 10 : 20;
printf("%d", y);

medium

A. 10

B. 20

C. 5

D. Syntax error

Solution

1. Step 1: Evaluate the condition (x > 3)

   Since x is 5, 5 > 3 is true.

2. Step 2: Apply ternary operator

   Because condition is true, y is assigned 10.

3. Final Answer:

   10 -> Option A

4. Quick Check:

   (5 > 3) ? 10 : 20 = 10 [OK]

Hint: Check if condition is true, then pick first value [OK]

Common Mistakes:

• Choosing the false value by mistake
• Confusing variable values
• Thinking it causes syntax error

4. Identify the error in this C code using the ternary operator:

int a = 10;
int b = 20;
int max = a > b ? a, b;

medium

A. Missing colon ':' between values

B. Incorrect variable declaration

C. No error, code is correct

D. Using comma instead of colon in ternary

Solution

1. Step 1: Check ternary operator syntax

   The ternary operator requires a colon ':' between the two possible values.

2. Step 2: Identify the mistake

   The code uses a comma ',' instead of a colon ':', which is incorrect syntax.

3. Final Answer:

   Using comma instead of colon in ternary -> Option D

4. Quick Check:

   Ternary needs ':' not ',' [OK]

Hint: Ternary uses ':' not ',' between values [OK]

Common Mistakes:

• Using comma instead of colon
• Forgetting colon entirely
• Assuming code is correct

5. Given this code snippet, what will be the value of result?

int a = 0;
int b = 5;
int result = (a != 0) ? (b / a) : (b * 2);
printf("%d", result);

hard

A. 0

B. Division by zero error

C. 10

D. 5

Solution

1. Step 1: Evaluate the condition (a != 0)

   a is 0, so (0 != 0) is false.

2. Step 2: Apply ternary operator

   Since condition is false, result is assigned (b * 2) = 5 * 2 = 10.

3. Final Answer:

   10 -> Option C

4. Quick Check:

   Condition false, so result = b*2 = 10 [OK]

Hint: Check condition first to avoid division by zero [OK]

Common Mistakes:

• Assuming division happens causing error
• Ignoring false condition path
• Confusing variable values