Question

Ruby has Enumerable#max and Enumerable#max_by and I am using max_by in the following way.

array = [
           {:a => 1, :b => 2, :c => 3}, 
           {:a => 3, :b => 2, :c => 4}, 
           {:a => 3, :b => 1, :c => 4}
        ]
max_item = array.max_by { |item| item[:b] }
=> {:b=>2, :c=>3, :a=>1}

So, it will return a single maximum (I think first), even though there are 2 items with same maximum value. I want to implement a function which gives both the items in such cases. Is there some other variant of max_by or do I need to write from scratch for this?

Answer 1

array = [
           {:a => 1, :b => 2, :c => 3}, 
           {:a => 3, :b => 2, :c => 4}, 
           {:a => 3, :b => 1, :c => 4}
        ]

array.group_by{|el| el[:b]}.max.last 
#=>[{:a=>1, :b=>2, :c=>3}, {:a=>3, :b=>2, :c=>4}]

group_by works a little too hard, but it does deliver.