Rosetta Code

Taxicab numbers

Search a small cube-sum table for numbers that can be written as two sums of two cubes.

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Sourcerosettacode/popular/taxicab_numbers.vibe
def sum_key(left: int, right: int) -> string
  "#{left ** 3 + right ** 3}"
end

def taxicab_numbers(limit: int) -> array<{ decompositions: array<array<int>>, value: string }>
  groups: hash<string, array<array<int>>> = {}
  order: array<string> = []
  left = 1

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

  rows: array<{ decompositions: array<array<int>>, value: string }> = []
  order.each { |key|
    if groups.fetch(key).length > 1
      rows << { value: key, decompositions: groups.fetch(key) }
    end
  }

  rows
end

def run -> array<{ decompositions: array<array<int>>, value: string }>
  taxicab_numbers(12).first(2)
end

Output

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