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//USE POINTER NOTATION
#include <iostream>
#include <cctype>
#include <cstring>
#include <cstdlib>
//#include <string>
using namespace std;

class Polynomial
{
private:
	int *coefficient;
	int counter;	
public:
	Polynomial()
	{
		coefficient = new int [1];
		*coefficient = '\0';
	}
	Polynomial(char *);
	//copyconstructor
	Polynomial(const Polynomial &obj)
	{
		counter = obj.counter;
		coefficient = new int[counter];
		for (int i = 0; i < counter; i++)
			*(coefficient + i) = obj.coefficient[i];
	}
	//destructor
	~Polynomial()
	{
		delete [] coefficient;
	}
	void setPolynomial(char *s);
	
	void getPolynomial() const
	{
		for (int i = 0; i < counter; i++)
		{			
			cout << coefficient[i] << "x^" << i;
			if (i != counter - 1)
				cout << " + ";
		}	
	}
	Polynomial operator + (const Polynomial &);
	Polynomial operator - (const Polynomial &);
	Polynomial operator * (const Polynomial &);
	const Polynomial operator=(const Polynomial &right)
	{;
		delete [] coefficient;
		counter = right.counter;
		coefficient = new int[counter];
		for (int i = 0; i < right.counter; i++)
			*(coefficient + i) = right.coefficient[i];
		return *this;
	}
};

int main()
{
	char input[50];
	char input2[50];
	
	cout << "Example: -4x^0 + x^1 + 0x^2+ 4x^3 + -3x^4" << endl;
	cout << "Enter a polynomial: ";
	cin.getline(input, 50);
	Polynomial one(input);
	cout << "Enter second polynomial: ";
	cin.getline(input2, 50);
	Polynomial two(input2);
	
	int choice;	
	do
	{
		cout << "1. Addition\n2. Subtraction\n3. Multiplication";
		cout << "\n4. Assignment\n5. Exit\nEnter your choice: ";
		cin >> choice;
		
		switch (choice)
		{
			case 1:
			{
				cout << "Addiction\n";
				Polynomial add = one + two;
				one.getPolynomial();
				cout << " + ";
				two.getPolynomial();
				cout << " = ";
				add.getPolynomial();	
				cout << endl;
			}
			break;
			case 2:
			{			
				cout << "Subtraction\n";
				Polynomial subtract = one - two;
				one.getPolynomial();
				cout << " - (";
				two.getPolynomial();
				cout << ") = ";
				subtract.getPolynomial();
				cout << endl;
			}
			break;
			case 3:
			{
				cout << "Multiplication\n";
				Polynomial multiply = one * two;
				one.getPolynomial();
				cout << " * (";
				two.getPolynomial();
				cout << ") = ";
				multiply.getPolynomial();
				cout << endl;
			}	
			break;
			case 4:
				cout << "Assignment\n";
				cout << "First polynomial: ";
				one.getPolynomial();
				cout << "\nSecond polynomial: ";
				two.getPolynomial();
				cout << "\nFirst = Second\nFirst polynomial is now: ";
				one = two;
				one.getPolynomial();
				cout << endl;
			break;
			case 5:
				cout << "Goodbye\n";
			break;
			default:
				cout << "Invalid choice\n";
			break;
		}
	}while (choice != 5);
	return 0;
}

Polynomial::Polynomial(char *s)
{
	char *string;
	string = new char [strlen(s) + 1];
	int length = strlen(string);
	strcpy(string, s);
	
	char *copy;
	copy = new char [length];
	strcpy(copy, string);
	
	char *p = strtok(string, "  +-");
	counter = 0;
	while (p) 
	{
	    p = strtok(NULL, "  +-");
		counter++;
	}
	
	coefficient = new int[counter];
	
	p = strtok(copy, "  +");
	int a = 0;
	while (p)
	{
		long int coeff;
		char *endptr;
	    coeff = strtol(p, &endptr, 10); //stops at first non number
		if (*p == 'x')
		   coeff = 1;

		coefficient[a] = coeff;
		p = strtok(NULL, "  +");
		a++;
	}
}

void Polynomial::setPolynomial(char *s)
{
	char *string;
	string = new char [strlen(s) + 1];
	int length = strlen(string);
	strcpy(string, s);
	
	char *copy;
	copy = new char[length];
	strcpy(copy, string);
	
	char *p = strtok(string, "  +-");
	counter = 0;
	while (p) 
	{
	    p = strtok(NULL, "  +-");
		counter++;
	}
	
	coefficient = new int[counter];
	
	p = strtok(copy, "  +");
	int a = 0;
	while (p)
	{
		long int coeff;
		char *endptr;
	    coeff = strtol(p, &endptr, 10); //stops at first non number
		if (*p == 'x')
		   coeff = 1;

		coefficient[a] = coeff;
		p = strtok(NULL, "  +");
		a++;
	}
}
Polynomial Polynomial::operator + (const Polynomial &right)
{
	Polynomial temp;
	//string, length, coefficient, counter
	int smallest, largest;
	smallest = (counter > right.counter) ? right.counter : counter;
	largest = (counter > right.counter) ? counter : right.counter;
	if (counter == right.counter)
		largest = counter;

	//make coefficient array
	temp.counter = largest;
	temp.coefficient = new int [largest];
	for (int i = 0; i < smallest; i++)
		temp.coefficient[i] = coefficient[i] + right.coefficient[i];
	for (int j = smallest; j < largest; j++)
	{
		if (counter > right.counter)
			temp.coefficient[j] = coefficient[j];
		else
			temp.coefficient[j] = right.coefficient[j];
	}
	return temp;
}
Polynomial Polynomial::operator - (const Polynomial &right)
{
	Polynomial temp;
	int smallest, largest;
	smallest = (counter > right.counter) ? right.counter : counter;
	largest = (counter > right.counter) ? counter : right.counter;
	if (counter == right.counter)
		largest = counter;

	//make coefficient array
	temp.counter = largest;
	temp.coefficient = new int [largest];
	for (int i = 0; i < smallest; i++)
		temp.coefficient[i] = coefficient[i] - right.coefficient[i];
	for (int j = smallest; j < largest; j++)
	{
		if (counter > right.counter)
			temp.coefficient[j] = coefficient[j];
		else
			temp.coefficient[j] = right.coefficient[j];
	}
	return temp;	
}
Polynomial Polynomial::operator * (const Polynomial &right)
{
	Polynomial temp;

	//make coefficient array
	int count = (counter + right.counter) - 1;
	temp.counter = count;
	temp.coefficient = new int [count];
	for (int i = 0; i < counter; i++)
	{
		for (int j = 0; j < right.counter; j++)
			temp.coefficient[i+j] += coefficient[i] * right.coefficient[j];
	}
	return temp;
}