Type casting in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of static_cast with integer to float

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

C++

int main() {
    int a = 5;
    float b = static_cast<float>(a) / 2;
    std::cout << b << std::endl;
    return 0;
}

A 2.0

B 2

C Compilation error

D 2.5

💡 Hint

Remember that static_cast changes the type before division.

Casting 'a' to float makes the division a floating-point division, so 5/2 becomes 2.5.

❓ Predict Output

intermediate

Output of reinterpret_cast on pointer

What will this C++ code print?

C++

#include <iostream>
int main() {
    int x = 65;
    char* p = reinterpret_cast<char*>(&x);
    std::cout << *p << std::endl;
    return 0;
}

A Undefined behavior

B A

C Compilation error

D 65

💡 Hint

Think about how integers are stored in memory and how char* reads bytes.

The integer 65 corresponds to ASCII 'A'. reinterpret_cast treats the int's address as char*, so *p reads the first byte, printing 'A'.

❓ Predict Output

advanced

Output of const_cast removing constness

What is the output of this code?

C++

#include <iostream>
int main() {
    const int a = 10;
    int* p = const_cast<int*>(&a);
    *p = 20;
    std::cout << a << std::endl;
    return 0;
}

A Undefined behavior

B 20

C Compilation error

D 10

💡 Hint

Modifying a const variable via const_cast is risky.

Changing a const variable through const_cast causes undefined behavior, so output is unpredictable.

❓ Predict Output

advanced

Output of dynamic_cast with polymorphism

What will this code print?

C++

#include <iostream>
class Base { public: virtual ~Base() {} };
class Derived : public Base {};
int main() {
    Base* b = new Base();
    Derived* d = dynamic_cast<Derived*>(b);
    if (d) std::cout << "Derived" << std::endl;
    else std::cout << "Null" << std::endl;
    delete b;
    return 0;
}

A Null

B Runtime error

C Compilation error

D Derived

💡 Hint

dynamic_cast returns nullptr if cast fails.

Since 'b' points to Base, not Derived, dynamic_cast returns nullptr, so output is 'Null'.

🧠 Conceptual

expert

Which cast is safest for downcasting polymorphic types?

In C++, when you want to safely convert a base class pointer to a derived class pointer, which cast should you use?

A static_cast

B reinterpret_cast

C dynamic_cast

D const_cast

💡 Hint

Consider runtime type checking.

dynamic_cast performs runtime checks and returns nullptr if the cast is invalid, making it safe for downcasting.