Determining if a number is either a multiple of ten or within a particular set of ranges

Question

I have a few loops that I need in my program. I can write out the pseudo code, but I\'m not entirely sure how to write them logically.

I need -

if (num is          


        

Answer 1

You might be overthinking this.

if (x % 10)
{
   .. code for 1..9 ..
} else
{
   .. code for 0, 10, 20 etc.
}

The first line if (x % 10) works because (a) a value that is a multiple of 10 calculates as '0', other numbers result in their remainer, (b) a value of 0 in an if is considered false, any other value is true.

Edit:

To toggle back-and-forth in twenties, use the same trick. This time, the pivotal number is 10:

if (((x-1)/10) & 1)
{
  .. code for 10, 30, ..
} else
{
   .. code for 20, 40, etc.
}

x/10 returns any number from 0 to 9 as 0, 10 to 19 as 1 and so on. Testing on even or odd -- the & 1 -- tells you if it's even or odd. Since your ranges are actually "11 to 20", subtract 1 before testing.