Question

I have any array of structs. Each struct in the array has the following attributes:

1. user_id
2. num_hot_dogs_eaten
3. date_last_pigged_out

Here’s what I want to do:

1. Find the structs with matching user_id’s, and merge them into one struct record where num_hot_dogs_eaten is the sum of all matching records and date_last_pigged_out is the most-recent date the user pigged out.

2. Sort the array of structs by num_hot_dogs_eaten (first order of priority) and by date_last_pigged_out (second order of priority…most-recent first).

3. Return a new sorted array of structs.

Answer 1

Use this:

def f(users)
  r = []
  users.each do |u|
    new_match = false
    match = r.find {|x| x.user_id == u.user_id }
    unless match
      match = u.dup
      r << match
      new_match = true
    end
    match.num_hot_dogs_eaten += u.num_hot_dogs_eaten unless new_match
    match.date_last_pigged_out =
      [match, u].max_by(&:date_last_pigged_out).date_last_pigged_out
  end
  r.sort_by {|u| [u.num_hot_dogs_eaten, u.date_last_pigged_out] }.
    reverse
end