group_by__and__sliding_window.rb

# group by x
# def time(a_proc)
#   start = Time.now
#   a_proc.call
#   puts Time.now - start
# end
#
# time(Proc.new { code_here })
# time(Proc.new { more_code_here })

# {'John' => [..], 'Linda' => [..]}

def group_by(data, key)
  data.each_with_object({ grouped_data: {}, problems: {} }) do |datum, acc|
    key_value = datum[key]
    if key_value == nil
      problem_key = "missing_#{key}"
      acc[:problems][problem_key] ||= []
      acc[:problems][problem_key] << datum
      next
    end
    acc[:grouped_data][key_value] ||= []
    acc[:grouped_data][key_value] << datum
    acc
  end
end

# p group_by([{ name: 'John' }, { name: 'Linda' }, { name: 'Linda' }, { a: 1 }], :name)
# {:grouped_data=>{"John"=>[{:name=>"John"}], "Linda"=>[{:name=>"Linda"}, {:name=>"Linda"}]}, :problems=>{"missing_name"=>[{:a=>1}]}}

# sliding window
def sliding_window(list, count)
  (0..list.size - count).map do |idx|
    # if idx + count >= list.size
    list[idx...(idx + count)]
  end
end

p sliding_window([1, 2, 3, 4], 2)
p sliding_window([1, 2, 3, 4], 3)
# [[1, 2, 3], [2, 3, 4]]