Types of inheritance in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Single Inheritance Example

What is the output of this C++ code demonstrating single inheritance?

C++

#include <iostream>
using namespace std;

class Animal {
public:
    void sound() { cout << "Animal sound" << endl; }
};

class Dog : public Animal {
public:
    void sound() { cout << "Dog barks" << endl; }
};

int main() {
    Dog d;
    d.sound();
    return 0;
}

A Dog barks\nAnimal sound

B Dog barks

C Compilation error

D Animal sound

💡 Hint

Look at which class's sound() method is called by the Dog object.

The Dog class overrides the sound() method of Animal. When calling d.sound(), Dog's version runs, printing 'Dog barks'.

❓ Predict Output

intermediate

Output of Multiple Inheritance Example

What is the output of this C++ code demonstrating multiple inheritance?

C++

#include <iostream>
using namespace std;

class Printer {
public:
    void print() { cout << "Printing document" << endl; }
};

class Scanner {
public:
    void scan() { cout << "Scanning document" << endl; }
};

class Copier : public Printer, public Scanner {
};

int main() {
    Copier c;
    c.print();
    c.scan();
    return 0;
}

A Scanning document

B Compilation error due to ambiguity

C Printing document

D Printing document\nScanning document

💡 Hint

Copier inherits both Printer and Scanner, so it can call both methods.

Copier inherits print() from Printer and scan() from Scanner. Both methods are called successfully, printing both lines.

❓ Predict Output

advanced

Output of Multilevel Inheritance with Overriding

What is the output of this C++ code demonstrating multilevel inheritance and method overriding?

C++

#include <iostream>
using namespace std;

class Vehicle {
public:
    virtual void start() { cout << "Vehicle starts" << endl; }
};

class Car : public Vehicle {
public:
    void start() override { cout << "Car starts" << endl; }
};

class SportsCar : public Car {
public:
    void start() override { cout << "SportsCar starts quickly" << endl; }
};

int main() {
    Vehicle* v = new SportsCar();
    v->start();
    delete v;
    return 0;
}

A Vehicle starts

B Car starts

C SportsCar starts quickly

D Compilation error due to override

💡 Hint

Virtual functions allow the most derived class's method to run through base class pointer.

Because start() is virtual, calling v->start() where v points to SportsCar runs SportsCar's start(), printing 'SportsCar starts quickly'.

❓ Predict Output

advanced

Output of Hierarchical Inheritance with Method Calls

What is the output of this C++ code demonstrating hierarchical inheritance?

C++

#include <iostream>
using namespace std;

class Shape {
public:
    void draw() { cout << "Drawing shape" << endl; }
};

class Circle : public Shape {
public:
    void draw() { cout << "Drawing circle" << endl; }
};

class Square : public Shape {
public:
    void draw() { cout << "Drawing square" << endl; }
};

int main() {
    Circle c;
    Square s;
    c.draw();
    s.draw();
    return 0;
}

A Drawing circle\nDrawing square

B Drawing shape\nDrawing shape

C Drawing circle\nDrawing shape

D Compilation error due to draw() redefinition

💡 Hint

Each derived class has its own draw() method that hides the base class method.

Circle and Square override draw(). Calling draw() on their objects prints their own messages, not the base class's.

🧠 Conceptual

expert

Diamond Problem in Multiple Inheritance

In C++, what problem arises in multiple inheritance when two base classes inherit from the same grandparent class, and a derived class inherits from both base classes? What is the typical solution?

A Ambiguity in accessing grandparent members; solved by virtual inheritance

B Compilation error due to duplicate class names; solved by renaming classes

C Runtime error due to conflicting constructors; solved by deleting one base class

D No problem arises; multiple inheritance always works without issues

💡 Hint

Think about how many copies of the grandparent class exist in the derived class.

The diamond problem causes ambiguity because the derived class inherits two copies of the grandparent class. Virtual inheritance ensures only one shared copy exists, resolving ambiguity.

Practice

1. Which type of inheritance involves a single derived class inheriting from one base class in C++?

easy

A. Hierarchical inheritance

B. Multiple inheritance

C. Multilevel inheritance

D. Single inheritance

Solution

1. Step 1: Understand inheritance types

   Single inheritance means one class inherits from exactly one base class.

2. Step 2: Match definition to options

   Only Single inheritance describes a single derived class inheriting from one base class.

3. Final Answer:

   Single inheritance -> Option D

4. Quick Check:

   One derived, one base = Single inheritance [OK]

Hint: One derived from one base is single inheritance [OK]

Common Mistakes:

• Confusing multiple inheritance with single inheritance
• Thinking multilevel means one base class only
• Mixing hierarchical with single inheritance

2. Which of the following is the correct syntax for multiple inheritance in C++?

easy

A. class Derived : public Base1 & Base2 {};

B. class Derived : public Base1, public Base2 {};

C. class Derived : Base1 Base2 {};

D. class Derived inherits Base1, Base2 {};

Solution

1. Step 1: Recall multiple inheritance syntax

   In C++, multiple inheritance uses commas to separate base classes with access specifiers.

2. Step 2: Check each option

   class Derived : public Base1, public Base2 {}; uses correct syntax: 'class Derived : public Base1, public Base2 {};'. Others have syntax errors.

3. Final Answer:

   class Derived : public Base1, public Base2 {}; -> Option B

4. Quick Check:

   Comma separates base classes with access specifiers [OK]

Hint: Use commas and access specifiers for multiple inheritance [OK]

Common Mistakes:

• Omitting commas between base classes
• Using '&' instead of commas
• Writing 'inherits' keyword which doesn't exist in C++

3. What will be the output of the following C++ code?

class A { public: void show() { std::cout << "A"; } };
class B : public A { public: void show() { std::cout << "B"; } };
class C : public B {};
int main() {
  C obj;
  obj.show();
  return 0;
}

medium

A. B

B. A

C. C

D. Compilation error

Solution

1. Step 1: Understand inheritance chain

   Class C inherits from B, which inherits from A. B overrides show() method.

2. Step 2: Determine which show() is called

   Calling obj.show() on C calls B's show() because C inherits B's version and does not override it.

3. Final Answer:

   B -> Option A

4. Quick Check:

   Derived class method called if overridden [OK]

Hint: Derived class method overrides base method unless not overridden [OK]

Common Mistakes:

• Assuming base class method runs instead of overridden
• Expecting 'C' output though C has no show()
• Thinking code causes compilation error

4. Identify the error in this C++ code snippet involving inheritance:

class Base { public: int x; };
class Derived : Base {};
int main() {
  Derived d;
  d.x = 1;
  return 0;
}

medium

A. Main function missing return type

B. Base class must be declared inside Derived

C. Missing access specifier before Base in Derived class

D. Derived class cannot be empty

Solution

1. Step 1: Check inheritance syntax

   In C++, inheritance requires an access specifier like public, private, or protected before base class name.

2. Step 2: Identify the error

   Derived : Base {} lacks access specifier; should be Derived : public Base {}.

3. Final Answer:

   Missing access specifier before Base in Derived class -> Option C

4. Quick Check:

   Inheritance needs access specifier [OK]

Hint: Always specify public/private/protected before base class [OK]

Common Mistakes:

• Omitting access specifier in inheritance
• Thinking empty class body is error
• Confusing return type in main function

5. Given the following classes:

class Animal { public: void eat() { std::cout << "Eating"; } };
class Mammal : public Animal {};
class Bird : public Animal {};
class Bat : public Mammal, public Bird {};
int main() {
  Bat b;
  b.eat();
  return 0;
}

What problem arises and how to fix it?

hard

A. Ambiguity error due to multiple inheritance; fix with virtual inheritance

B. No problem; code runs fine

C. Syntax error in Bat class declaration

D. eat() method must be overridden in Bat

Solution

1. Step 1: Analyze inheritance structure

   Bat inherits Mammal and Bird, both inherit Animal, causing two Animal copies in Bat.

2. Step 2: Identify ambiguity

   Calling b.eat() is ambiguous because Bat has two Animal parts; compiler error occurs.

3. Step 3: Fix with virtual inheritance

   Use virtual inheritance for Mammal and Bird from Animal to share one Animal base.

4. Final Answer:

   Ambiguity error due to multiple inheritance; fix with virtual inheritance -> Option A

5. Quick Check:

   Diamond problem fixed by virtual inheritance [OK]

Hint: Use virtual inheritance to solve diamond ambiguity [OK]

Common Mistakes:

• Ignoring diamond problem ambiguity
• Thinking code compiles without error
• Assuming method override fixes ambiguity