Taxicab numbers

# title: Taxicab numbers
# source: https://rosettacode.org/wiki/Taxicab_numbers
# category: Rosetta Code
# difficulty: Medium
# summary: Search a small cube-sum table for numbers that can be written as two sums of two cubes.
# tags: popular, math, search, cubes
# vibe: 0.2

def cube(value)
  value * value * value
end

def sum_key(left, right)
  "" + (cube(left) + cube(right))
end

def taxicab_numbers(limit)
  groups = {}
  order = []
  left = 1

  while left <= limit
    right = left
    while right <= limit
      key = sum_key(left, right)
      if groups[key] == nil
        groups[key] = []
        order = order.push(key)
      end
      groups[key] = groups[key].push([left, right])
      right = right + 1
    end
    left = left + 1
  end

  rows = []
  index = 0
  while index < order.length
    key = order[index]
    if groups[key].length > 1
      rows = rows.push({
        value: key,
        decompositions: groups[key]
      })
    end
    index = index + 1
  end

  rows
end

def run
  taxicab_numbers(12).first(2)
end