def quick_sort(a)

    return a if a.size < 2
    (x = a.pop) ?  quick_sort(a.select{|i| i <=x }) + [x] + quick_sort(a.select{|i| i > x}) : []
end
array = [72,6,57,88,60,42,83,73,42,48,85]
p quick_sort(array)    #=> [6, 42, 42, 48, 57, 60, 72, 73, 83, 85, 88]

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