C++ : Inheritance with BASE & DERIVED Classes

Inheritance allows us to define a class in terms of another class, which makes it easier to create and maintain an application. This also provides an opportunity to reuse the code functionality and fast implementation time.

The programmer can designate that the new class should inherit the members of an existing class. This existing class is called the base class, and the new class is referred to as the derived class.

The idea of inheritance implements the is a relationship. For example, mammal IS-A animal, dog IS-A mammal hence dog IS-A animal as well and so on.

Base & Derived Classes:

A class can be derived from more than one classes, which means it can inherit data and functions from multiple base classes. To define a derived class, we use a class derivation list to specify the base class(es). A class derivation list names one or more base classes and has the form:

class derived-class: access-specifier base-class

Where access-specifier is one of public, protected, or private, and base-class is the name of a previously defined class. If the access-specifier is not used, then it is private by default.

Consider a base class Shape and its derived class Rectangle as follows:

#include <iostream>
 
using namespace std;

// Base class
class Shape 
{
   public:
      void setWidth(int w)
      {
         width = w;
      }
      void setHeight(int h)
      {
         height = h;
      }
   protected:
      int width;
      int height;
};

// Derived class
class Rectangle: public Shape
{
   public:
      int getArea()
      { 
         return (width * height); 
      }
};

int main(void)
{
   Rectangle Rect;
 
   Rect.setWidth(5);
   Rect.setHeight(7);

   // Print the area of the object.
   cout << "Total area: " << Rect.getArea() << endl;

   return 0;
}

When the above code is compiled and executed, it produces following result:

Total area: 35

Multiple Inheritances:

A C++ class can inherit members from more than one class and here is the extended syntax:

class derived-class: access baseA, access baseB....

Where access is one of public, protected, or private and would be given for every base class and they will be separated by comma as shown above. Let us try the following example:

#include <iostream>
 
using namespace std;

// Base class Shape
class Shape 
{
   public:
      void setWidth(int w)
      {
         width = w;
      }
      void setHeight(int h)
      {
         height = h;
      }
   protected:
      int width;
      int height;
};

// Base class PaintCost
class PaintCost 
{
   public:
      int getCost(int area)
      {
         return area * 70;
      }
};

// Derived class
class Rectangle: public Shape, public PaintCost
{
   public:
      int getArea()
      { 
         return (width * height); 
      }
};

int main(void)
{
   Rectangle Rect;
   int area;
 
   Rect.setWidth(5);
   Rect.setHeight(7);

   area = Rect.getArea();
   
   // Print the area of the object.
   cout << "Total area: " << Rect.getArea() << endl;

   // Print the total cost of painting
   cout << "Total paint cost: $" << Rect.getCost(area) << endl;

   return 0;
}

When the above code is compiled and executed, it produces following result:

Total area: 35
Total paint cost: $2450

When deriving a class from a base class, the base class may be inherited through public, protected orprivate inheritance. The type of inheritance is specified by the access-specifier as explained above.

We hardly use protected or private inheritance but public inheritance is commonly used. While using different type of inheritance, following rules are applied:


Public Inheritance: When deriving a class from a public base class, public members of the base class become public members of the derived class and protected members of the base class become protected members of the derived class. A base class's private members are never accessible directly from a derived class, but can be accessed through calls to the publicand protected members of the base class.


Protected Inheritance: When deriving from a protected base class, public and protectedmembers of the base class become protected members of the derived class.


Private Inheritance: When deriving from a private base class, public and protected members of the base class become private members of the derived class.

Exercise-1: Write a c++ program using Inheritance to check whether the given integer number is palindrome or not ?

Exercise-2: Given a range [a,b], you are to  find the summation of all the odd integers in this range. For example,the summation of all the odd integers in the range [3,9] is 3 + 5 + 7 + 9 = 24. View Details:

Exercise-3: Mohammad has recently visited Switzerland. As he loves his friends very much, he decided to buy some chocolate for them, but as this fine chocolate is very ex-pensive (You know Mohammad is a little BIT stingy!), he could only afford buying one chocolate, albeit a very big one (part of it can be seen in  figure  below) for all of them as a souvenir. Now, he wants to give each of his friends exactly one part of this chocolate and as he believes all human beings are equal (!), he wants to split it into equal parts.The chocolate is an M x N rectangle constructed from M x N unit-sized squares. You can assume that Mohammad has also M x N friends waiting to receive their piece of chocolate. To split the chocolate, Mohammad can cut it in vertical or horizontal direction (through the lines that separate the squares). Then, he should do the same with each part separately until he
reaches M x N unit size pieces of chocolate. Unfortunately, because he is a little lazy, he wants to use the minimum number of cuts required to accomplish this task.Your goal is to tell him the minimum number of cuts needed to split all of the chocolate squares apart. View Details: