Remove redundant or duplicate tuples in Ruby array

Question

Imagine the following Ruby array:

[9, 9, 5, 5, 5, 2, 9, 9]

What's the easiest way of removing redundant tuples, producing an output like the following:

[9, 5, 2, 9]

uniq is not correct because it's examining the entire array. The ordering of the input is important and must be kept. Is there a straightforward approach to this?

Thanks!

Answer 1

I'd do using Enumerable#chunk

2.0.0-p0 :001 > a = [9, 9, 5, 5, 5, 2, 9, 9]
 => [9, 9, 5, 5, 5, 2, 9, 9] 
2.0.0-p0 :002 > a.chunk { |e| e }.map(&:first)
 => [9, 5, 2, 9]

Answer 2

I would do it like

b = [];
a.each { |n| b << n if b.last != n }

and b is the result

only one array scan is needed