Determine if one array contains all elements of another array

Question

I need to tell if an array contains all of the elements of another array with duplicates.

[1,2,3].contains_all? [1,2]   #=> true
[1,2,3].contains_all         


        

Answer 1

class Array
  def contains_all? other
    other = other.dup
    each{|e| if i = other.index(e) then other.delete_at(i) end}
    other.empty?
  end
end

Answer 2

Counting the number of occurrences and comparing them seems to be the obvious way to go.

class Array
   def contains_all? arr
       h = self.inject(Hash.new(0)) {|h, i| h[i] += 1; h}
       arr.each do |i|
           return false unless h.has_key?(i)
           return false if h[i] == 0
           h[i] -= 1
       end
       true
   end
end

Answer 3

Answering with my own implementation, but definitely want to see if someone can come up with a more efficient way. (I won't accept my own answer)

class Array
  def contains_all?(a2)
    a2.inject(self.dup) do |copy, el|
      if copy.include? el
        index = copy.index el
        copy.delete_at index
      else
        return false
      end
      copy
    end
    true
  end
end

And the tests:

1.9.3p194 :016 > [1,2,3].contains_all? [1,2]   #=> true
 => true 
1.9.3p194 :017 > [1,2,3].contains_all? [1,2,2] #=> false (this is where (a1-a2).empty? fails)
 => false 
1.9.3p194 :018 > [2,1,2,3].contains_all? [1,2,2] #=> true
 => true 

Answer 4

class Array
  def contains_all?(ary)
    ary.uniq.all? { |x| count(x) >= ary.count(x) }
  end
end

test

irb(main):131:0> %w[a b c c].contains_all? %w[a b c]
=> true
irb(main):132:0> %w[a b c c].contains_all? %w[a b c c]
=> true
irb(main):133:0> %w[a b c c].contains_all? %w[a b c c c]
=> false
irb(main):134:0> %w[a b c c].contains_all? %w[a]
=> true
irb(main):135:0> %w[a b c c].contains_all? %w[x]
=> false
irb(main):136:0> %w[a b c c].contains_all? %w[]
=> true

The following version is faster and shorter in code.

class Array
  def contains_all?(ary)
    ary.all? { |x| count(x) >= ary.count(x) }
  end
end

Answer 5

If you can't find a method, you can build one using ruby's include? method.

Official documentation: http://www.ruby-doc.org/core-1.9.3/Array.html#method-i-include-3F

Usage:

array = [1, 2, 3, 4]
array.include? 3       #=> true

Then, you can do a loop:

def array_includes_all?( array, comparision_array )
  contains = true
  for i in comparision_array do
    unless array.include? i
      contains = false
    end
  end
  return contains
end

array_includes_all?( [1,2,3,2], [1,2,2] )    #=> true

Answer 6

This solution will only iterate through both lists once, and hence run in linear time. It might however be too much overhead if the lists are expected to be very small.

  class Array
    def contains_all?(other)
      return false if other.size > size
      elem_counts = other.each_with_object(Hash.new(0)) { |elem,hash| hash[elem] += 1 }
      each do |elem|
        elem_counts.delete(elem) if (elem_counts[elem] -= 1) <= 0
        return true if elem_counts.empty?
      end
      false
    end
  end