Rainforest QA

accounts.sql

-- accounts
-- ========
-- id
-- email
-- 
-- pricing_plans
-- ===========
-- id
-- price_in_cents
-- 
-- account_pricing_plans
-- ==================
-- id
-- account_id
-- pricing_plan_id
-- start_time
-- end_time

SELECT accounts.id
FROM accounts
JOIN account_pricing_plans ON accounts.id = account_pricing_plans.account_id
JOIN pricing_plans ON pricing_plans.id = account_pricing_plans.pricing_plan_id
WHERE pricing_plans.price_in_cents = 100;

unique_pairs.rb

def unique_pairs(array)
  output = []

  array = array.uniq

  array.each_with_index do |n, i|
    array.each_with_index do |m, j|
      if i != j && n + m == 100
        result = []
        result[0] = [n, m].min
        result[1] = [n, m].max
        output << result
      end
    end
  end

  output.uniq
end

#> input = [1, 27, 50, 49, 51, 99, 51, 51]
#> unique_pairs(input)
# => [[1, 99], [49, 51]]