Ruby – Set Operations

The set is an unordered collection with no duplicate items. Like other languages, Ruby also provides a set class that represents the mathematical notion of a set. Here, we will discuss the basic set operations, i.e., Union, Intersection, and Difference.

Union

In Ruby, the union takes two objects like arrays, vectors, hashes, etc. as arguments and results in a third object which contains all the elements from both the objects and removes duplicate elements. You can perform a union between two arrays using the pipe operator(|).

Syntax:
x | y

Parameters: x and y are the sequence items of objects.

For Example:

[1, 2, 1, 2, 3, 5, 7] | [1, 2, 3, 4] #=> [1, 2, 3, 4, 5, 7]

Example 1:

# Ruby program to illustrate the union

# Array
arr_1 = [ 2, 4, 5, 6, 7, 9, 1, 2, 4 ]
arr_2 = [ 2, 4, 5, 6, 9, 8, 0, 3, 3 ]

# Union
 result = arr_1 | arr_2

 # Display result
 puts "#{result}"

Output:

[2, 4, 5, 6, 7, 9, 1, 8, 0, 3]

Example 2:

# Ruby program to illustrate Union of arrays

class MultiSet
  attr_accessor :set
  def initialize(set)
    @set = set
  end

# Union
  def |(other)
    @set | other.set
  end
end

x = MultiSet.new([ 1, 1, 2, 2, 3, 4, 5, 6, 7, 8 ])
y = MultiSet.new([ 1, 3, 5, 6, 8 ])

p x | y

Output:

[1, 2, 3, 4, 5, 6, 7, 8]

Intersection

In Ruby, intersection takes two objects like arrays, vectors, hashes, etc. as arguments and results in a third object which contains elements that are common in both the objects and remove duplicates. The order in the intersection is preserved from the original array. You can perform intersection either by using & operator or by using the intersection() function.

Syntax:
x & y

Parameters: x and y are the sequence items of objects.

For Example:

[ 'a', 'b', 'b', 'z' ] & [ 'a', 'b', 'c' ,'z']   #=> [ 'a', 'b' ,'z']

Example 1:

# Ruby program to illustrate the intersection method

# requires the set
require "set"

x = Set.new([ 1, 2, 3, 4 ])
y = Set.new([ 1, 2, 4 ])

# Intersection method used
res = x.intersection(y)

# Prints the res
puts res

Output:

Set: {1, 2, 4}

Example 2:

# Ruby program to illustrate intersection of arrays
class MultiSet
  attr_accessor :set
  def initialize(set)
    @set = set
  end

# Intersection
  def &(other)
    @set & other.set
  end

x = MultiSet.new([ 1, 1, 2, 2, 3, 4, 5, 6, 7, 8 ])
y = MultiSet.new([ 1, 3, 5, 6, 8 ])

p x & y
end

Output:

[1, 3, 5, 6, 8]

Difference

In Ruby, difference takes two objects like arrays, vectors, hashes, etc. as arguments and returns the difference of both the objects. You can perform difference either by using – operator or by using the difference() function.

Syntax:
x – y

Parameters: x and y are the sequence items of objects.

For Example:

[ 22, 45, 89, 76 ] - [ 22, 22, 89, 79 ]   #=> [45]

Example 1:

# Ruby program to illustrate the difference method

# requires the set
require "set"

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

# Difference method used
res = x.difference(y)

# Prints the res
puts res

Output:

Set: {3}

Example 2:

# Ruby program to illustrate difference of arrays
class MultiSet
  attr_accessor :set
  def initialize(set)
    @set = set
  end

# Difference
  def -(other)
    @set - other.set
  end

x = MultiSet.new([ 1, 1, 2, 2, 3, 4, 5, 6, 7, 8 ])
y = MultiSet.new([ 1, 3, 5, 6, 8 ])

p x - y
end

Output:

[2, 2, 4, 7]