gistfile1.txt

main):009:0> quick(10_000) { x.inject({}) {|a,b| (a[b.first] ||= []) << b.last ; a }.map(&:flatten) }
Rehearsal ------------------------------------
   0.290000   0.040000   0.330000 (  0.334947)
--------------------------- total: 0.330000sec

       user     system      total        real
   0.310000   0.020000   0.330000 (  0.327561)
=> nil
(main):010:0> quick(10_000) { Hash[*x].map { |k, v| [k.first, k.last, v.last] } }
Rehearsal ------------------------------------
   0.120000   0.020000   0.140000 (  0.135189)
--------------------------- total: 0.140000sec

       user     system      total        real
   0.110000   0.020000   0.130000 (  0.143096)
=> nil