缘由既约分数，除了辗转相除法-编程语言-CSDN问答

void 判断既约分数()
{
	int a = 1, b = 2020, aa = b, y = 2, gs = 0;
	while (aa)
	{
		while (a <= b)
		{
			while (y <= a && y <= aa)
			if (a%y == 0 && aa%y == 0)
				++a, y = 2;
			else
				++y;
			if (a <= b)++gs; else;
			++a, y = 2;
		}
		a = 1, --aa;
	}
	//std::cout << "\n" << gs << "\n";
    printf("%d", gs);
}

void 判断既约分数()
{
	int a = 1, b = 20, aa = 1, y = 2, gs = 0;
	while (aa <= b)
	{
		while (a <= b)
		{
			while (y <= a && y <= aa)
			if (a%y == 0 && aa%y == 0)
				++a, y = 2;
			else
				++y;
			if (a <= b)std::cout << a << "/" << aa << "\t";
			if (a <= b)++gs; else;
			++a, y = 2;
		}
		a = 1, ++aa;
		std::cout << "\n";
	}
	std::cout << "\n" << gs << "\n";
}