Is there a class that represents an unordered array in Ruby? I cannot use array because:
[1,2] != [2,1]
And I cannot use set because I can only have unique elements. I want a kind of both combinations. A list that doesn't care about ordering and can have more than 1 of the same element.
It is called multiset. Here is Ruby implementation.
I guess you have extend the Array class and write your own == method. Here is my very experimental attempt:
class UnorderedArray < Array
def ==(other)
self_copy = self.sort
other = other.sort
self_copy == other
end
end
a = UnorderedArray.new
a << 1 << 2
# [1, 2]
b = UnorderedArray.new
b << 2 << 1
# [2, 1]
a == b
# returns true
Here is a slightly cleaner mixin that will work on unsortable arrays and caches the hash value as it is O(n).
class UnorderedArray < Array
def hash
unless @o && @o == super.hash
p = Hash.new(0)
each{ |v| p[v] += 1 }
@p = p.hash
@o = super.hash
end
@p.hash
end
def <=>(b)
raise "You can't order me"
end
def ==(b)
hash == b.hash
end
end
however #eql? will return false unless unless the arrays are in the same order.
One-liner:
Hash[a.zip(a.map{|x| a.count(x)})] == Hash[e.zip(e.map{|x| e.count(x)})]
