Project Euler-Problem 1

RubyEuler1.rb

# Given a maximum integer m and a factor n, calculates the sum
# of all divisors of n up to m.
def sumDivisible(m,n)
	p = m / n
	n * (p * (p + 1)) / 2
end

def solve
	result = sumDivisible(999,3) + sumDivisible(999,5) - sumDivisible(999, 15)
	"The sum of multiples of 3 and 5 up to 1000 is: #{result}"
end

# Naive alternative solution based on filtering a range.
def alternative(j,k,m)
	sum = 0
	1.upto(m-1) do |n|
		if n % j == 0 || n % k == 0 then
			sum += n
		end
	end
	sum
end

puts solve