高精度减法与混合加法

高精度减法

bigNum bigSub(bigNum* a, bigNum* b)
{
	bigNum c;
	for (int i = 0; i < a->len || i < b->len; i++)
	{
		if (a->num[i] < b->num[i])
		{
			a->num[i] += 10;
			a->num[i + 1] -= 1;
		}
		c.num[i] = a->num[i] - b->num[i];
	}
	while (c.num[c.len - 1] == 0&&c.len>=1)
		c.len--;
	return c;
}

注意：只能实现结果为正，故使用前需用比较

混合加法

bigNum smallMul(bigNum* a, int b)
{
	int carry = 0; int len = a->len;
	bigNum c;
	for (int i = 0; i < len; i++)
	{
		int temp = b * a->num[i] + carry;
		c.num[c.len++] = temp % 10;
		carry = temp / 10;
	}
	while (carry != 0)
	{
		c.num[c.len++] = carry % 10;
		carry = carry / 10;
	}
	return c;
}