Ternary operator in C - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested ternary operator

What is the output of this C code snippet?

C

int x = 5, y = 10;
int result = x > y ? x : y > 7 ? y : x;
printf("%d", result);

A 5

B 10

C 7

D Compilation error

💡 Hint

Remember how nested ternary operators are evaluated from left to right.

The expression evaluates as x > y ? x : (y > 7 ? y : x). Since x=5 is not greater than y=10, it checks y > 7 which is true, so result is y=10.

❓ Predict Output

intermediate

Ternary operator with side effects

What will be printed by this code?

C

int a = 3, b = 4;
int c = (a > b) ? (a += 2) : (b += 3);
printf("%d %d %d", a, b, c);

A 3 4 4

B 5 4 5

C Compilation error

D 3 7 7

💡 Hint

Check which condition is true and how the variables change.

Since a=3 is not greater than b=4, the else part runs: b += 3 makes b=7, c=7, a remains 3.

❓ Predict Output

advanced

Ternary operator with pointer dereference

What is the output of this code?

C

int x = 10, y = 20;
int *p = (x > y) ? &x : &y;
printf("%d", *p);

A 10

B 0

C 20

D Segmentation fault

💡 Hint

Check which pointer is assigned based on the condition.

Since x=10 is not greater than y=20, pointer p points to y, so *p is 20.

❓ Predict Output

advanced

Ternary operator with different types

What will this code print?

C

int a = 5;
float b = 3.5;
float c = (a > 3) ? a : b;
printf("%.1f", c);

A 5.0

B Compilation error

C 5

D 3.5

💡 Hint

The ternary operator promotes types to a common type.

Since a=5 > 3, c is assigned a converted to float 5.0, so it prints 5.0.

🧠 Conceptual

expert

Ternary operator associativity

Consider the expression: int x = 1 ? 0 ? 2 : 3 : 4; What is the value of x after this executes?

A 3

B 2

C 4

D Compilation error

💡 Hint

Ternary operators associate right to left in C.

Expression groups as: 1 ? (0 ? 2 : 3) : 4. Since 1 is true, evaluate (0 ? 2 : 3) which is 3, so x=3.

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