238. Product of Array Except Self

# @param {Integer[]} nums
# @return {Integer[]}
def product_except_self(nums)
  result = []
  buffer = 1
  result[0] = buffer

  (1...nums.size).each { |i| result[i] = nums[i - 1] * result[i - 1]}

  (nums.size - 1).downto(0).each { |e| result[e] = result[e] * buffer; buffer = buffer * nums[e] }

  result
end