You can subtract arrays in Ruby:
[1,2,3,4,5] - [1,3,4] #=> [2,5]
ary – other_ary → new_ary Array Difference
Returns a new array that is a copy of the original array, removing any
items that also appear in other_ary. The order is preserved from the
original array.It compares elements using their hash and eql? methods for efficiency.
[ 1, 1, 2, 2, 3, 3, 4, 5 ] - [ 1, 2, 4 ] #=> [ 3, 3, 5 ]If you need
set-like behavior, see the library class Set.
See the Array documentation.