Returning all maximum or minimum values that can be multiple

Question

Enumerable#max_by and Enumerable#min_by return one of the relevant elements (presumably the first one) when there are multiple max

Answer 1

This is the hash equivalent of @Serio's use of group_by.

arr = [1, 2, 3, 5]

arr.each_with_object(Hash.new { |h,k| h[k] = [] }) { |e,h| h[e%3] << e }.max.last
  #=> [2, 5]

The steps:

h = arr.each_with_object(Hash.new { |h,k| h[k] = [] }) { |e,h| h[e%3] << e }
  #=> {1=>[1], 2=>[2, 5], 0=>[3]}
a = h.max
  #=> [2, [2, 5]]
a.last
  #=> [2, 5]