Ruby: Count unique elements and their occurences in an array

標籤：

Is there a method in Ruby that takes an array, and counts all unique elements and their occurrences and passes them back as a hash?

For example

  [‘A‘,‘A‘,‘A‘,‘A‘,‘B‘,‘B‘,‘C‘].method> {‘A‘ => 4, ‘B‘ => 2, ‘C‘ => 1}

Something like that.

[‘A‘,‘A‘,‘A‘,‘A‘,‘B‘,‘B‘,‘C‘].group_by{|e| e}.map{|k, v| [k, v.length]}.to_h

src = [‘A‘,‘A‘,‘A‘,‘A‘,‘B‘,‘B‘,‘C‘]Hash[src.group_by { |x| x }.map { |k, v| [k, v.length] }]
counts = Hash.new(0)[‘A‘,‘A‘,‘A‘,‘A‘,‘B‘,‘B‘,‘C‘].each { |name| counts[name] += 1 }counts   => {"A"=>4, "B"=>2, "C"=>1}


[‘A‘,‘A‘,‘A‘,‘A‘,‘B‘,‘B‘,‘C‘].each_with_object(Hash.new(0)) { |l, o| o[l] += 1 }

            
This is the easiest readable for me:
src = [‘A‘,‘A‘,‘A‘,‘A‘,‘B‘,‘B‘,‘C‘]src.group_by(&:to_s).to_a.map { |a| [a[0], a[1].count] }.to_h
Or here is another solution with reduce method:
src.reduce({}) { |b, a| b.merge({a => (b[a] || 0) + 1}) }
Or:
src.reduce(Hash.new(0)) { |b, a| b.merge({a => b[a] + 1}) }
    

Ruby: Count unique elements and their occurences in an array