# Project Euler #1 Pseudocode

### The Challenge

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.

#### What Does It Mean?

We need to add up all the numbers between 1 and 1000 (but not 1000) which are an multiple of 3 or 5. The easiest way would to have a loop with a two step test for the multiple. Pass a test, get added to the sum. If we can pull off both tests in one line, that should speed things up. Maybe use a Mod3 and Mod5 if it’s available for the language? Well, let’s get some pseudocode

We should probably define some variables and some includes, depending on the language.

```include needed stuff

current_num
sum

loop start at 1 go to less than 1000
check if current_num is multiple of 3?
If false, is current_num a multiple of 5?
If false, test next number

print sum
exit program```

Should I have it print each step of the tests? Might be a good idea for the test versions? Maybe add a –quiet/q flag and the option to set the max value to test up to?

### UPDATE

I rewrote the code a bit, here it is:

```include needed stuff

# Define vars early if we need to. Use them in first time in blocks if allowed
current_num
sum

loop start at 1 go to less than 1000
check if current_num is multiple of 3 or 5