# Euler Problem No. 1
#  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.

#function that determines if a number is a multiple of 3 or 5
def div_by_3_or_5 (num)
	if num%3==0 || num%5==0 then
		num
	else
		0
	end
end

#naturals is an array that holds all natural numbers from 1 to 999 that are multiples of 3 or 5
naturals = Array.new
for x in 1...1000 #  . . . denotes not inclusive of the upper bound
	if div_by_3_or_5(x) != 0 then
		naturals << x
	end
end

#sum up the numbers in the array, then output the sum
ret = naturals.inject(0) {|x,n| x+n}
print "#{ret} is the sum \n"

#another way is to simply add the values, it's just not as fun
ret2 = 0
for y in 1...1000
	ret2 = ret2 + div_by_3_or_5(y)
end
print "#{ret2} is the sum\n"