challenge: count even substring

count_even_substrings.rb

# frozen_string_literal: true

# quickstart
#
# ruby count_even_substrings.rb

def count_even_substrings(str)
  j = 0
  size = str.size
  acc = []

  loop do
    i = 1
    even_substring({ acc: acc, size: size, str: str, i: i, j: j })
    break if j >= (size - 1)

    j += 1
  end
  acc.any? ? acc.size : -1
end

def even_substring(params)
  loop do
    substr = params[:str].slice(params[:j], params[:i])
    params[:acc] << substr if substr.to_i.even?
    break if params[:i] > (params[:size] - (params[:j] + 1))

    params[:i] += 1
  end
end

p count_even_substrings('56789') # 6
p count_even_substrings('5847548') # 18
p count_even_substrings('5555555') # -1

output.txt

6
18
-1