Constants and literals in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of const and literal usage

What is the output of this C++ code snippet?

C++

#include <iostream>
int main() {
    const int x = 5;
    constexpr int y = 10;
    int z = x + y;
    std::cout << z << std::endl;
    return 0;
}

A Undefined behavior

B 510

C Compilation error

D 15

💡 Hint

Remember that const and constexpr values can be used in expressions.

The const int x and constexpr int y are both constants. Adding them results in 15, which is printed.

❓ Predict Output

intermediate

Integer literal suffix effect

What is the output of this C++ code?

C++

#include <iostream>
int main() {
    auto a = 10u;
    auto b = 5;
    std::cout << (a - b) << std::endl;
    return 0;
}

A Compilation error

B Unsigned integer wrap-around value

C -5

D 5

💡 Hint

Check the types of a and b and how subtraction works.

a is unsigned int (10u), b is int (5). Subtracting 5 from 10u results in unsigned arithmetic, which can cause wrap-around if b is larger. Here, 10u - 5 is 5, so the output is 5.

❓ Predict Output

advanced

Floating-point literal precision

What is the output of this C++ code snippet?

C++

#include <iostream>
#include <iomanip>
int main() {
    float f = 1.23456789f;
    double d = 1.23456789;
    std::cout << std::setprecision(9) << f << " " << d << std::endl;
    return 0;
}

A 1.23456788 1.23456789

B Compilation error

C 1.23456789 1.23456788

D 1.23456789 1.23456789

💡 Hint

Float has less precision than double.

The float variable loses precision and prints 1.23456788, while double keeps 1.23456789.

❓ Predict Output

advanced

Character literal and integer conversion

What is the output of this C++ code?

C++

#include <iostream>
int main() {
    char c = 'A';
    int i = c + 1;
    std::cout << i << std::endl;
    return 0;
}

A A1

B Compilation error

C 66

D 65

💡 Hint

Character literals are stored as integer ASCII codes.

'A' has ASCII code 65, adding 1 results in 66 printed as integer.

🧠 Conceptual

expert

Constant expression evaluation

Which of the following declarations is NOT a valid constant expression in C++?

A constexpr int z = rand();

B const int y = 10 * 2;

C constexpr int x = 5 + 3;

D constexpr int w = 7 - 4;

💡 Hint

Constant expressions must be evaluable at compile time.

rand() is a runtime function, so constexpr int z = rand(); is invalid as a constant expression.