n本の様々な長さの棒の中から3本使って、できるだけ周長の長い三角形を作る | ruby pythagorean.rb n（省略時：15）

pythagorean.rb

class Pythagorean
  
  def initialize(n)
    @sticks  = [ *1 .. ( { 0 => 15 }[n] || n ) ]
    @triples = @sticks.map(&:to_f).combination(3)
  end

  def triples
    @triples.select( &theorem ).map { |e| e.map(&:to_i) }
  end
  
  def theorem
    lambda { |args| Math.hypot(*args[0..1]) == args[2] }
  end
    
  def triples_groupby_length
    triples.group_by { |e| e.inject(:+) }
  end
  
  def triples_of_maxlength(&block)
    result = triples_groupby_length.max
    block_given? ? yield(result) : result
  end
  
  def triples_groupby_gcd
    triples.group_by { |a, b, c| gcd = a.gcd(b).gcd(c)  ; [a, b, c].map { |e| e / gcd }  }
  end
  
end

if __FILE__ == $0

  n = ARGV[0].to_i
  
  pythagorean = Pythagorean.new(n)
  
  # p pythagorean.triples_groupby_gcd.keys

  pythagorean.triples_of_maxlength do |length, triples|
  
    len  = length || "N/A"
    list = triples ? triples.map(&:inspect) * "," : "N/A"
    
    puts <<-OUTPUT
    MaxLength: #{ len  }
      Triples: #{ list }
  
    OUTPUT
  
  end

end