Splitting an array into subarrays - arrays

Question

I have an array of chars that looks like this:
chars = ["x", "o", "o", "x", "x", "o", "o", "x", "x", "x", "o", "o"]
I need to get the number of consecutive chars and the index of that char. It should look like this:
[
{ index: 0, length: 1 }, # "x"
{ index: 1, length: 2 }, # "o", "o"
{ index: 3, length: 2 }, # "x", "x"
{ index: 5, length: 2 }, # "o", "o"
{ index: 7, length: 3 }, # "x", "x", "x"
{ index: 10, length: 2 } # "o", "o"
]
Is there an easy way to achieve this?

Answer 1

Not sure if you'd call this an easy way, but here's a one-line way of doing it. Resulting array is of the form [index, length].
chars.each_with_index.chunk {|i, _| i}.map {|_, y| [y.first.last, y.length]}
#=> [[0, 1], [1, 2], [3, 2], [5, 2], [7, 3], [10, 2]]

Answer 2

Two others ways of doing it:
Use Emumerable#slice_when (v.2.2+)
count = 0
arr = chars.slice_when { |a,b| a != b }.map do |arr|
sz = arr.size
h = { index: count, length: sz }
count += sz
h
end
#=> [{:index=>0, :length=>1}, {:index=>1, :length=>2}, {:index=>3, :length=>2},
# {:index=>5, :length=>2}, {:index=>7, :length=>3}, {:index=>10, :length=>2}]
Use a regex with a backreference
count = 0
arr = chars.join.scan(/((.)\2*)/).map do |run, _|
sz = run.size
h = { index: count, length: sz }
count += sz
h
end
#=> [{:index=>0, :length=>1}, {:index=>1, :length=>2}, {:index=>3, :length=>2},
# {:index=>5, :length=>2}, {:index=>7, :length=>3}, {:index=>10, :length=>2}]