Ruby: Count unique elements and their occurences in an array
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)
counts => {"A"=>4, "B"=>2, "C"=>1}
['A','A','A','A','B','B','C'].each { |name| counts[name] += 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_hOr 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}) }
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