Rational

#include <bits/stdc++.h>
using namespace std;

int gcd(int a, int b) {
    if (!b)
        return a;
    return gcd(b, a % b);
}

class Rational {
private:
    int p;
    int q;
public:
    Rational() {
        p = 0;
        q = 1;
    }
    Rational(int numerator, int denominator) {
        if (numerator == 0) {
            p = 0;
            q = 1;
        } else {
            bool is_positive = (numerator * denominator > 0);
            p = (is_positive) ?
                    abs(numerator) / gcd(abs(numerator), abs(denominator)) :
                    (-1) * abs(numerator)
                            / gcd(abs(numerator), abs(denominator));
            q = abs(denominator) / gcd(abs(numerator), abs(denominator));
        }
    }

    int Numerator() const {
        return p;
    }
    int Denominator() const {
        return q;
    }
};

Rational operator+(const Rational &lhs, const Rational &rhs) {
    if (lhs.Denominator() != rhs.Denominator()) {
        return Rational(
                lhs.Numerator() * rhs.Denominator()
                        + rhs.Numerator() * lhs.Denominator(),
                lhs.Denominator() * rhs.Denominator());
    }
    return Rational(lhs.Numerator() + rhs.Numerator(), lhs.Denominator());
}

Rational operator-(const Rational &lhs, const Rational &rhs) {
    if (lhs.Denominator() != rhs.Denominator()) {
        return Rational(
                lhs.Numerator() * rhs.Denominator()
                        - rhs.Numerator() * lhs.Denominator(),
                lhs.Denominator() * rhs.Denominator());
    }
    return Rational(lhs.Numerator() - rhs.Numerator(), lhs.Denominator());
}

bool operator==(const Rational &lhs, const Rational &rhs) {
    return (lhs.Numerator() == rhs.Numerator())
            && (lhs.Denominator() == rhs.Denominator());
}

//mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());

int main(void) {
    {
        Rational r1(4, 6);
        Rational r2(2, 3);
        bool equal = r1 == r2;
        if (!equal) {
            cout << "4/6 != 2/3" << endl;
            return 1;
        }
    }

    {
        Rational a(2, 3);
        Rational b(4, 3);
        Rational c = a + b;
        bool equal = c == Rational(2, 1);
        if (!equal) {
            cout << "2/3 + 4/3 != 2" << endl;
            return 2;
        }
    }

    {
        Rational a(5, 7);
        Rational b(2, 9);
        Rational c = a - b;
        bool equal = c == Rational(31, 63);
        if (!equal) {
            cout << "5/7 - 2/9 != 31/63" << endl;
            return 3;
        }
    }

    cout << "OK" << endl;
    return 0;
}