Ruby array sorting: getting all the elements that have the max value while chaining methods (namely,-CodePudding

Suppose that after sorting an array with a custom block you need to get all the elements that have the max value.

A common method would be to use Enumerable#take_while like this

array = [ 1, 3, 2, 3, 2, 3 ].sort {|a,b| b - a}
array.take_while { |e| e == array[0] }
#=> [3, 3, 3]

Now, when you are beautifully chaining methods and don't want to stop the chain just for storing the sorted array (which you'll need for referencing its first element in the take_while block), how would you do it?

_{I posted the question and an answer for reference, but I probably missed better ways, so feel free to post your own method}

CodePudding user response：

My own response to the question is to use Enumerable#slice_when like this

[ 1, 3, 2, 3, 2, 3 ].sort {|a,b| b - a}.slice_when {|a,b| b != a}.first
#=> [3, 3, 3]

note: Performance wise it seems OK since slice_when returns an Enumerator.

With ruby >= 2.5, combining @engineersmnky and @Cary methods

[ 1, 3, 2, 3, 2, 3 ].then { |arr| mx = arr.max; arr.select { |elm| elm == mx } }
#=> [3, 3, 3]

CodePudding user response：

You can try this

pry(main)> [ 1, 2, 2, 3, 3, 3 ].sort.slice_when {|a,b| b > a}.to_a.last 
=> [3, 3, 3]

A bit similar of the last solution but also different.

Source https://ruby-doc.org/core-3.0.2/Enumerable.html#method-i-slice_when