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) : ((x == y) ? 0 : (y - x));
std::cout << result << std::endl;

A 0

B -5

C 5

D 10

💡 Hint

Remember the ternary operator evaluates conditions from left to right.

Since x (5) is not greater than y (10), the first condition is false. Then it checks if x == y, which is false. So it returns y - x, which is 10 - 5 = 5.

❓ Predict Output

intermediate

Ternary operator with side effects

What will be printed by this C++ code?

C++

int a = 3, b = 4;
int c = (a > b) ? (a += 2) : (b += 3);
std::cout << a << " " << b << " " << c << std::endl;

A 3 7 7

B 5 4 5

C 5 7 7

D 3 4 3

💡 Hint

Check which condition is true and which variable is updated.

Since a (3) is not greater than b (4), the else part runs, so b is increased by 3 to 7, and c gets the value 7. a remains 3.

🧠 Conceptual

advanced

Understanding ternary operator associativity

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

A 2

B 0

C 3

D 1

💡 Hint

Ternary operators associate from right to left.

The expression is parsed as int x = 1 ? 0 : (1 ? 2 : 3); Since 1 is true, x is assigned 0.

❓ Predict Output

advanced

Ternary operator with different types

What is the output of this code snippet?

C++

auto val = true ? 3.5 : 2;
std::cout << typeid(val).name() << " " << val << std::endl;

A d 3.5

B i 2

C f 3.5

D i 3

💡 Hint

Check the type deduced by the ternary operator when operands have different types.

The ternary operator promotes int 2 to double 2.0, so val is double (typeid name 'd') and value 3.5.

🔧 Debug

expert

Identify the error in ternary operator usage

Which option will cause a compilation error in this code snippet?

C++

int a = 5, b = 10;
int result = (a > b) ? a : "10";
std::cout << result << std::endl;

A int result = (a > b) ? a : static_cast<int>(10);

B int result = (a > b) ? a : (int)10;

C int result = (a > b) ? a : 10;

D int result = (a > b) ? a : "10";

💡 Hint

Check the types of the values returned by the ternary operator.

Option D uses a string literal "10" which cannot be assigned to int result, causing a compilation error.