How can I get the intersection union and subset of arrays in Ruby

Question

I want to create different methods for a class called Multiset   I have all the required methods  but I m unsure of how to write intersection  union  and subset methods   For intersection and union  my code starts like this   def intersect var    x   Multiset new end   Here is an example   X    1  1  2  4  Y    1  2  2  2    then the intersection of X and Y is  1  2

User · Accepted Answer

Utilizing the fact that you can do set operations on arrays by doing &(intersection), -(difference), and |(union).

Obviously I didn't implement the MultiSet to spec, but this should get you started:

class MultiSet
  attr_accessor :set
  def initialize(set)
    @set = set
  end
  # intersection
  def &(other)
    @set & other.set
  end
  # difference
  def -(other)
    @set - other.set
  end
  # union
  def |(other)
    @set | other.set
  end
end

x = MultiSet.new([1,1,2,2,3,4,5,6])
y = MultiSet.new([1,3,5,6])

p x - y # [2,2,4]
p x & y # [1,3,5,6]
p x | y # [1,2,3,4,5,6]

User · Answer

If Multiset extends from the Array class  x    1  1  2  4  7  y    1  2  2  2  z    1  1  3  7    UNION  x union y                gt   1  2  4  7        ONLY IN RUBY 2 6  x union y  z             gt   1  2  4  7  3     ONLY IN RUBY 2 6  x   y                    gt   1  2  4  7    DIFFERENCE  x difference y           gt   4  7   ONLY IN RUBY 2 6  x difference y  z        gt   4   ONLY IN RUBY 2 6  x - y                    gt   4  7    INTERSECTION  x  amp  y                    gt   1  2    For more info about the new methods in Ruby 2 6  you can check this blog post about its new features

User · Answer

I assume X and Y are arrays  If so  there s a very simple way to do this   x    1  1  2  4  y    1  2  2  2     intersection x  amp  y                gt   1  2     union x   y                gt   1  2  4     difference x - y                gt   4    Source

[ruby] How can I get the intersection, union, and subset of arrays in Ruby?

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