Euler Project Problem #021

euler21.rb

# Solution to Project Euler's twenty-first problem
# http://projecteuler.net/index.php?section=problems&id=21
# Find the sum of the amicable pairs below 10000.
def generate_sum_of_divisors(ceiling)
	sums = Array.new(ceiling+1, 0)
	(0..ceiling).each do |number|
		(1..Math.sqrt(number)).each do |num|
			if number % num == 0 then
				sums[number] += num
				if number/num != num && num != 1 then
					sums[number] += number/num
				end
			end
		end
	end
	return sums 
end
def generate_amicable_numbers(sums)
	array = [] 
	sums.each_with_index do |sum, i|
		if sums[sum] != nil && sum == sums[i] && i == sums[sum] && i != sum then
					array << i
		end
	end
	return array
end
a = Time.new


number = 10000 
sums = generate_sum_of_divisors(number)
amicable_pairs = generate_amicable_numbers(sums)
p amicable_pairs.inject(0) { |result, element| result + element }
b = Time.new - a
p b