Edit Question - KnowledgeHub

Title Body

assuming I have the following array: views = [ { :user_id => 1, :viewed_at => '2012-06-29 17:03:28 -0400' }, { :user_id => 1, :viewed_at => '2012-06-29 17:04:28 -0400' }, { :user_id => 2, :viewed_at => '2012-06-29 17:05:28 -0400' }, { :user_id => 3, :viewed_at => '2012-06-29 17:06:28 -0400' }, { :user_id => 1, :viewed_at => '2012-06-29 17:07:28 -0400' }, { :user_id => 1, :viewed_at => '2012-06-29 17:08:28 -0400' }, { :user_id => 3, :viewed_at => '2012-06-29 17:09:28 -0400' }, { :user_id => 3, :viewed_at => '2012-06-29 17:16:28 -0400' }, { :user_id => 3, :viewed_at => '2012-06-29 17:26:28 -0400' }, { :user_id => 3, :viewed_at => '2012-06-29 17:36:28 -0400' }, { :user_id => 1, :viewed_at => '2012-06-29 17:47:28 -0400' }, { :user_id => 2, :viewed_at => '2012-06-29 17:57:28 -0400' }, { :user_id => 3, :viewed_at => '2012-06-29 17:67:28 -0400' }, { :user_id => 1, :viewed_at => '2012-06-29 17:77:28 -0400' } ] assuming the array is ordered by viewed_at If I want to retrieve the last view hash in the views array for a particular user_id , I could do the following: views.reverse.detect { |view| view[:user_id] == 1 } where detect would returns first item in an enumerable where the block evaluates to true. My question is: I assume there is O(n) cost to the reverse method, so how can I detect in reverse without having to reverse the array? Or is the reverse method not O(n) ?

Tags (comma-separated) Cancel