Answer to Question #344577 in C++ for khan

Question

Task 2:(Inheritance and Polymorphism)

We want to calculate the total marks of each student of a class in Physics, Chemistry and

Mathematics and the average marks of the class. The number of students in the class are entered by the user. Create a class named Marks with data members for roll number, name and marks. Create three other classes inheriting the Marks class, namely Physics, Chemistry and Mathematics, which are used to define marks in individual subject of each student. Roll number of each student will be generated automatically.

Answer 1

#include <iostream>
#include <cmath>

using namespace std;

class Marks {
public:
	int rollNumber;
	char *name;
	int *marks; // array of marks

	int num_marks; // number of the marks

	void GenerateMarks(int num) { // fills the array with marks
		num_marks = num;
		marks = new int[num];

		for (int i = 0; i < num; i++)
			marks[i] = rand() % 5 + 1;
	}

	int sum_of_marks() {
		int sum = 0;

		for (int i = 0; i < num_marks; i++)
			sum += marks[i];

		return sum;
	}

	double avarage() {
		return round(((double)sum_of_marks() / num_marks) * 100) / 100;
	}

	void set_marks(int number_of_marks, int newmarks) { // change mark with number number_of_marks
		marks[number_of_marks] = newmarks;
	}

	int get_marks(int number_of_marks) {
		return marks[number_of_marks];
	}

	void set_num_marks(int num) {
		num_marks = num;
		
		delete[]marks;

		marks = new int[num];
	}

	~Marks() {
		delete[]marks;
	}

};


class Physics : public Marks {
public:
	
};


class Chemistry : public Marks {
public:


};


class Mathematics : public Marks {
public:


};

int main()
{
	int num;

	cout << "Enter the number of students ";
	cin >> num;

	Physics *cl1_phys = new Physics[num]; // array of student with marks in physics
	Chemistry *cl1_chem = new Chemistry[num]; // array of student with marks in chemistry
	Mathematics *cl1_math = new Mathematics[num]; // array of student with marks in mathematics

	for (int i = 0; i < num; i++) { // Generate marks and roll numbers

		cl1_phys[i].rollNumber = cl1_chem[i].rollNumber = cl1_math[i].rollNumber = i + 1;

		cl1_phys[i].GenerateMarks(9);
		cl1_chem[i].GenerateMarks(5);
		cl1_math[i].GenerateMarks(2);
	}


	cout << "\nThe total marks of each student of a class in Physics, Chemistry and Mathematics: \n\n";

	for (int i = 0; i < num; i++) { // sums of marks
		cout << "Roll number of student is " << cl1_phys[i].rollNumber << endl;

		cout << "The total marks in Physics is " << cl1_phys[i].sum_of_marks() << endl;
		cout << "The total marks in Chemistry is " << cl1_chem[i].sum_of_marks() << endl;
		cout << "The total marks in Mathematics is " << cl1_math[i].sum_of_marks() << endl;

		cout << endl;
	}

	cout << endl << "--------------------------" << endl;

	cout << "\nThe average marks : \n\n";

	for (int i = 0; i < num; i++) { // averages of marks
		cout << "Roll number of student is " << cl1_phys[i].rollNumber << endl;

		cout << "The average mark in Physics is " << cl1_phys[i].avarage() << endl;
		cout << "The average mark in Chemistry is " << cl1_chem[i].avarage() << endl;
		cout << "The average mark in Mathematics is " << cl1_math[i].avarage() << endl;

		cout << endl;
	}

	return 0;
}