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

arr=[1, 2, 3, 5, 7, 8]
mods=arr.map{|e| e%3}

find max

max=mods.max
indices = []
mods.each.with_index{|m, i| indices << i if m.eql?(max)}
arr.select.with_index{|a,i| indices.include?(i)}

find min

min = mods.min
indices = []
mods.each.with_index{|m, i| indices << i if m.eql?(min)}
arr.select.with_index{|a,i| indices.include?(i)}

Sorry for clumsy code, will try to make it short.

Answer by @Sergio Tulentsev is the best and efficient answer, found things to learn there. +1