Types of inheritance in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a class Dog that inherits publicly from class Animal.

C++

class Dog : [1] Animal {
public:
    void bark() {
        std::cout << "Woof!" << std::endl;
    }
};

Drag options to blanks, or click blank then click option'

Apublic

Bprivate

Cprotected

Dvirtual

Attempts:

3 left

💡 Hint

Common Mistakes

Using private inheritance hides base class public members.

Forgetting to specify inheritance type defaults to private in classes.

In C++, public inheritance means the public members of the base class remain public in the derived class.

2fill in blank

medium

Complete the code to show multiple inheritance where class SmartPhone inherits from both Phone and Camera.

C++

class SmartPhone : [1] Phone, [2] Camera {
public:
    void use() {
        call();
        takePhoto();
    }
};

Drag options to blanks, or click blank then click option'

Apublic

Bprivate

Cprotected

Dvirtual

Attempts:

3 left

💡 Hint

Common Mistakes

Using different inheritance types for each base class.

Using private inheritance which hides base class members.

Multiple inheritance uses the same access specifier for each base class; public inheritance keeps members accessible.

3fill in blank

hard

Fix the error in the code to correctly implement multilevel inheritance where Car inherits from Vehicle and ElectricCar inherits from Car.

C++

class Vehicle {
public:
    void start() { std::cout << "Vehicle started" << std::endl; }
};

class Car : [1] Vehicle {
public:
    void drive() { std::cout << "Car driving" << std::endl; }
};

class ElectricCar : public Car {
public:
    void charge() { std::cout << "Charging battery" << std::endl; }
};

Drag options to blanks, or click blank then click option'

Apublic

Bvirtual

Cprotected

Dprivate

Attempts:

3 left

💡 Hint

Common Mistakes

Using private inheritance which restricts access to base class members.

Omitting inheritance specifier defaults to private in classes.

Public inheritance allows the derived class to access public members of the base class.

4fill in blank

hard

Fill both blanks to create a hierarchical inheritance where Teacher and Student both inherit from Person.

C++

class Teacher : [1] Person {};
class Student : [2] Person {};

Drag options to blanks, or click blank then click option'

Apublic

Bprivate

Cprotected

Dvirtual

Attempts:

3 left

💡 Hint

Common Mistakes

Using private inheritance which hides base class members.

Mixing different inheritance types for the two classes.

Both classes should inherit publicly from Person to keep Person's public members accessible.

5fill in blank

hard

Fill all three blanks to implement hybrid inheritance combining multiple and multilevel inheritance.

C++

class A {
public:
    void funcA() { std::cout << "A" << std::endl; }
};

class B : [1] A {
public:
    void funcB() { std::cout << "B" << std::endl; }
};

class C : [2] A {
public:
    void funcC() { std::cout << "C" << std::endl; }
};

class D : [3] B, public C {
public:
    void funcD() { std::cout << "D" << std::endl; }
};

Drag options to blanks, or click blank then click option'

Apublic

Bprivate

Cprotected

Dvirtual

Attempts:

3 left

💡 Hint

Common Mistakes

Using private inheritance which hides base class members.

Mixing inheritance types causing access issues.

Public inheritance is used throughout to keep all base class members accessible in derived classes.

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