# Two stage array sorting **URL:** \ **Category:** Ruby\ **Created:** [October 30, 2009, 5:34pm UTC](https://www.ruby-forum.com/t/two-stage-array-sorting/178197 "2009-10-30T17:34:57Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![s0nspark](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f475e1/32.png) [@s0nspark](https://www.ruby-forum.com/u/s0nspark)\ **Post date:** [October 30, 2009, 5:34pm UTC](https://www.ruby-forum.com/t/two-stage-array-sorting/178197/1 "2009-10-30T17:34:57Z")
I have an array of strings like so: Tuesday 12:00 AM Sunday 9:00 AM Tuesday 3:00 PM Friday 7:30 AM Wednesday 5:00 PM and I want the array sorted by day name and then time. Is it possible to do this without resorting to a two stage process? Currently I am breaking the array out into arrays by day and sorting those by time and then reassembling… it just feels dirty 🙂 Ideas? Thanks much… ---
**Author:** ![s0nspark](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f475e1/32.png) [@s0nspark](https://www.ruby-forum.com/u/s0nspark)\ **Post date:** [October 30, 2009, 6:12pm UTC](https://www.ruby-forum.com/t/two-stage-array-sorting/178197/2 "2009-10-30T18:12:18Z")
Tim F. wrote: > I have an array of strings like so: > > Tuesday 12:00 AM > Sunday 9:00 AM > Tuesday 3:00 PM > Friday 7:30 AM > Wednesday 5:00 PM > > and I want the array sorted by day name and then time. Is it possible to > do this without resorting to a two stage process? Currently I am > breaking the array out into arrays by day and sorting those by time and > then reassembling… it just feels dirty 🙂 > > Ideas? array.sort\_by{|s| s.split(’ ')} Of couse, that will do alphabetic sorting in each half. If you need time sorting, my suggestion would be to use a date parsing function in the sort\_by block. > Thanks much… ## Best, Marnen Laibow-Koser [http://www.marnen.org](http://www.marnen.org) removed\_email\_address@domain.invalid ---
**Author:** ![s0nspark](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f475e1/32.png) [@s0nspark](https://www.ruby-forum.com/u/s0nspark)\ **Post date:** [October 30, 2009, 6:19pm UTC](https://www.ruby-forum.com/t/two-stage-array-sorting/178197/3 "2009-10-30T18:19:25Z")
Morning Tim, On Fri, Oct 30, 2009 at 9:35 AM, Tim F. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > do this without resorting to a two stage process? Currently I am > breaking the array out into arrays by day and sorting those by time and > then reassembling… it just feels dirty 🙂 require ‘date’ def sort\_datetime\_array(ary) fmt = ‘%A %I:%M %p’ ary.sort{ |a,b| DateTime.strptime(a, fmt) \<=\> DateTime.strptime(b, fmt) } end c = [‘Friday 1:00 PM’, ‘Tuesday 12:00 AM’, ‘Wednesday 3:00 PM’, ‘Tuesday 11:59 PM’] puts sort\_datetime\_array(c) –output– Tuesday 12:00 AM Tuesday 11:59 PM Wednesday 3:00 PM Friday 1:00 PM Just note that the original array is not sorted in this case - the method returns a new sorted array - if you wanted the sorting done in place then change sort to sort! in the method John ---
**Author:** ![s0nspark](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f475e1/32.png) [@s0nspark](https://www.ruby-forum.com/u/s0nspark)\ **Post date:** [October 30, 2009, 6:44pm UTC](https://www.ruby-forum.com/t/two-stage-array-sorting/178197/4 "2009-10-30T18:44:27Z")
Perfect … thanks so much! Cheers, Tim John W Higgins wrote: > require ‘date’ > > def sort\_datetime\_array(ary) > fmt = ‘%A %I:%M %p’ > ary.sort{ |a,b| > DateTime.strptime(a, fmt) \<=\> DateTime.strptime(b, fmt) > } > end ---
**Author:** ![s0nspark](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f475e1/32.png) [@s0nspark](https://www.ruby-forum.com/u/s0nspark)\ **Post date:** [October 30, 2009, 11:59pm UTC](https://www.ruby-forum.com/t/two-stage-array-sorting/178197/5 "2009-10-30T23:59:11Z")
John W Higgins wrote: > Morning Tim, > > On Fri, Oct 30, 2009 at 9:35 AM, Tim F. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > > do this without resorting to a two stage process? Currently I am > > breaking the array out into arrays by day and sorting those by time and > > then reassembling… it just feels dirty 🙂 > > require ‘date’ > > def sort\_datetime\_array(ary) > fmt = ‘%A %I:%M %p’ > ary.sort{ |a,b| > DateTime.strptime(a, fmt) \<=\> DateTime.strptime(b, fmt) > } > end > > c = [‘Friday 1:00 PM’, ‘Tuesday 12:00 AM’, ‘Wednesday 3:00 PM’, ‘Tuesday > 11:59 PM’] > puts sort\_datetime\_array(c) > > –output– > Tuesday 12:00 AM > Tuesday 11:59 PM > Wednesday 3:00 PM > Friday 1:00 PM > > Just note that the original array is not sorted in this case - the > method > returns a new sorted array - if you wanted the sorting done in place > then > change sort to sort! in the method > > John In this case, sort\_by is faster because it creates less DateTime objects. def sort\_by\_datetime(ary) ary.sort\_by {|el| Date.strptime(el, ‘%A %I:%M %p’) } end (see the ri for enumerable#sort\_by ). Hth, Siep ---
**Author:** ![s0nspark](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f475e1/32.png) [@s0nspark](https://www.ruby-forum.com/u/s0nspark)\ **Post date:** [October 31, 2009, 12:10am UTC](https://www.ruby-forum.com/t/two-stage-array-sorting/178197/6 "2009-10-31T00:10:46Z")
On Oct 30, 10:35 am, Tim F. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I have an array of strings like so: > > Tuesday 12:00 AM > Sunday 9:00 AM > Tuesday 3:00 PM > Friday 7:30 AM > Wednesday 5:00 PM > > and I want the array sorted by day name and then time. Is it possible to > do this without resorting to a two stage process? Although you already have better answers specific to your needs, the answer to this question is also yes: class Array; def rand; self[Kernel.rand(length)]; end; end Person = Struct.new( :first, :last, :age ) do def to\_s; “#{last}, #{first} - #{age}”; end end FIRSTS = %w[Gavin Lisa John Joe Jim Jill Bob Anne Zach Michael] LASTS = %w[Jones Smith Jackson] people = (0…40).map{ Person.new( FIRSTS.rand, LASTS.rand, rand (60) ) } # Name ascending, age descending puts people.sort\_by{ |who| [who.last, who.first, -who.age] } #=\> Jackson, Anne - 28 #=\> Jackson, Anne - 22 #=\> Jackson, Bob - 29 #=\> Jackson, Bob - 9 #=\> Jackson, Gavin - 54 #=\> Jackson, Jim - 12 #=\> Jackson, Jim - 9 #=\> Jackson, Jim - 1 #=\> Jackson, Joe - 47 #=\> Jackson, John - 41 #=\> Jackson, Lisa - 8 #=\> Jackson, Zach - 38 #=\> Jones, Anne - 52 #=\> Jones, Bob - 48 #=\> Jones, Bob - 15 #=\> Jones, Bob - 6 #=\> Jones, Gavin - 30 #=\> Jones, Jill - 35 #=\> Jones, Jim - 50 #=\> Jones, Jim - 49 #=\> Jones, Jim - 44 #=\> Jones, Jim - 3 #=\> Jones, Joe - 35 #=\> Jones, Joe - 11 #=\> Jones, Joe - 4 #=\> Jones, John - 37 #=\> Jones, John - 10 #=\> Jones, Zach - 21 #=\> Jones, Zach - 2 #=\> Smith, Anne - 20 #=\> Smith, Bob - 48 #=\> Smith, Gavin - 4 #=\> Smith, Jill - 56 #=\> Smith, Jill - 39 #=\> Smith, Jill - 25 #=\> Smith, Jill - 2 #=\> Smith, Jim - 7 #=\> Smith, Joe - 49 #=\> Smith, John - 44 #=\> Smith, John - 29 #=\> Smith, John - 28 ---
**Author:** ![s0nspark](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f475e1/32.png) [@s0nspark](https://www.ruby-forum.com/u/s0nspark)\ **Post date:** [October 31, 2009, 12:08am UTC](https://www.ruby-forum.com/t/two-stage-array-sorting/178197/7 "2009-10-31T00:08:25Z")
On Oct 30, 11:17 am, John W Higgins [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > I have an array of strings like so: > > then reassembling… it just feels dirty 🙂 > > require ‘date’ > > def sort\_datetime\_array(ary) > fmt = ‘%A %I:%M %p’ > ary.sort{ |a,b| > DateTime.strptime(a, fmt) \<=\> DateTime.strptime(b, fmt) > } > end Note that using sort is much slower than using sort\_by (though perhaps slightly more memory-efficient). This is possibly only significant if you’re sorting large amount of items, however. I mostly prefer sort\_by because it is DRYer (and hence less typing :). require ‘date’ require ‘benchmark’ class Array; def rand; self[Kernel.rand(length)]; end; end DAYS = %w[Monday Tuesday Wednesday Thursday Friday Saturday Sunday] AMPM = %w[AM PM] FORMAT = ‘%A %I:%M %p’ Benchmark.bmbm do |x| [10,100,1\_000,10\_000].each do |n| a = (0…n).map{ “#{DAYS.rand} #{rand(12)+1}:#{rand(60)} # {AMPM.rand}” } x.report( “sort #{n}”) do a.sort{ |y,z| Date.strptime(y,FORMAT) \<=\> Date.strptime (z,FORMAT) } end x.report( “sort\_by #{n}”) do a.sort\_by{ |y| Date.strptime(y,FORMAT) } end end end #=\> Rehearsal ------------------------------------------------- #=\> sort 10 0.020000 0.000000 0.020000 ( 0.020270) #=\> sort\_by 10 0.000000 0.000000 0.000000 ( 0.003464) #=\> sort 100 0.200000 0.000000 0.200000 ( 0.204563) #=\> sort\_by 100 0.030000 0.000000 0.030000 ( 0.032382) #=\> sort 1000 2.390000 0.040000 2.430000 ( 2.455060) #=\> sort\_by 1000 0.300000 0.010000 0.310000 ( 0.316943) #=\> sort 10000 19.700000 0.280000 19.980000 ( 20.197492) #=\> sort\_by 10000 3.270000 0.060000 3.330000 ( 3.361712) #=\> --------------------------------------- total: 26.300000sec #=\> user system total real #=\> sort 10 0.020000 0.000000 0.020000 ( 0.016442) #=\> sort\_by 10 0.000000 0.000000 0.000000 ( 0.003143) #=\> sort 100 0.190000 0.000000 0.190000 ( 0.190505) #=\> sort\_by 100 0.030000 0.000000 0.030000 ( 0.026150) #=\> sort 1000 2.300000 0.030000 2.330000 ( 2.351752) #=\> sort\_by 1000 0.290000 0.010000 0.300000 ( 0.298472) #=\> sort 10000 19.020000 0.240000 19.260000 ( 19.437129) #=\> sort\_by 10000 3.310000 0.050000 3.360000 ( 3.389367)