Euler Project Problem #005

euler5.rb

# Solution to Project Euler's fifth problem
# http://projecteuler.net/index.php?section=problems&id=5
# Find the smallest number divisible with no remainder by each number below twenty.
def generate_primes(ceiling)
	primes, count = [1, 2], 1
	until primes.last > ceiling do
		numbers = (primes[count-1]**2+1..primes[count]**2).to_a
		1.upto(count) {|c| numbers.select! {|number| number%primes[c] != 0}}
		primes.concat(numbers)
		count += 1
	end
	primes.shift #remove 1
	until primes.last < ceiling 
		primes.pop #remove last
	end
	return primes
end
def generate_exponents(factors)
	ceiling = factors.last
	until factors.first == ceiling do
		if factors.first * factors.first < ceiling then
			first = factors[0]
			factors[0] = factors[0] * first
			while factors[0] < ceiling/2
				factors[0] = factors[0] * first
			end
		end
		factors.push factors.shift
		puts factors.last
	end
	return factors
end
number, smallest = 20, 1 
factors = generate_primes(number)
factors = generate_exponents(factors)
p factors
factors.each do |f|
smallest = smallest * f
end
puts smallest