Question

I need to merge consecutive repeating elements in an array, such that

[1, 2, 2, 3, 1]

becomes

[1, 2, 3, 1]

#uniq doesn’t work for this purpose. Why? Because #uniq will produce this:

[1, 2, 3]

Answer 1

def remove_consecutive_duplicates(xs)
  [xs.first] + xs.each_cons(2).select do |x,y|
    x != y
  end.map(&:last)
end

remove_consecutive_duplicates([1, 2, 2, 3, 1])
#=> [1,2,3,1]

This returns a new array like uniq does and works in O(n) time.