From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-08-05T23:02:40+09:00
Subject: Re: algorithm help

On Fri, 5 Aug 2005, Kroeger Simon (ext) wrote:

>
>> d = [1, 3, 4, 5, 6, 7, 8, 9, 15, 38, 39, 40, 41, 6789, 6790,
>> 9998, 9999]
>> puts d.inject([d[0]..d[0]]){|r,x|r<<(((r.last.end+1>=x)?r.pop.end:
>> x)..x)}
>
> erm, this has to be
>
> d = [1, 3, 4, 5, 6, 7, 8, 9, 15, 38, 39, 40, 41, 6789, 6790, 9998, 9999]
> puts d.inject([d[0]..d[0]]){|r,x|
>    r<<(((r.last.end+1>=x)?r.pop.first: x)..x)}

there are lots of failures with this however:


     harp:~ > ruby a.rb
     []                                    => bad value for range (bad value for range)
     [0]                                   =>                                [0..0]
     [0]                                   =>                                [0..0]
     [0, 1]                                =>                                [0..1]
     [1, 0]                                =>                                [1..0]
     [0, 1, 2]                             =>                                [0..2]
     [2, 1, 0]                             =>                                [2..0]
     [0, 1, 2, 3]                          =>                                [0..3]
     [3, 2, 1, 0]                          =>                                [3..0]
     [0, 3]                                =>                          [0..0, 3..3]
     [3, 0]                                =>                                [3..0]
     [0, 3, 5]                             =>                    [0..0, 3..3, 5..5]
     [5, 3, 0]                             =>                                [5..0]
     [0, 3, 5, 7]                          =>              [0..0, 3..3, 5..5, 7..7]
     [7, 5, 3, 0]                          =>                                [7..0]
     [0, 1, 3, 4]                          =>                          [0..1, 3..4]
     [4, 3, 1, 0]                          =>                                [4..0]
     [0, 1, 3, 4, 6, 7]                    =>                    [0..1, 3..4, 6..7]
     [7, 6, 4, 3, 1, 0]                    =>                                [7..0]
     [0, 1, 3, 4, 6, 7, 9, 10]             =>             [0..1, 3..4, 6..7, 9..10]
     [10, 9, 7, 6, 4, 3, 1, 0]             =>                               [10..0]
     [0, 1, 3, 4, 6, 7, 10]                =>            [0..1, 3..4, 6..7, 10..10]
     [10, 7, 6, 4, 3, 1, 0]                =>                               [10..0]
     [0, 3, 4, 6, 7, 9, 10]                =>             [0..0, 3..4, 6..7, 9..10]
     [10, 9, 7, 6, 4, 3, 0]                =>                               [10..0]
     [0, 1, 3]                             =>                          [0..1, 3..3]
     [3, 1, 0]                             =>                                [3..0]
     [0, 3, 4]                             =>                          [0..0, 3..4]
     [4, 3, 0]                             =>                                [4..0]
     [0, -1]                               =>                               [0..-1]
     [-1, 0]                               =>                               [-1..0]
     [0, -1, -2]                           =>                               [0..-2]
     [-2, -1, 0]                           =>                               [-2..0]
     [0, -1, -3, -4]                       =>                               [0..-4]
     [-4, -3, -1, 0]                       =>                       [-4..-3, -1..0]
     [0, -1, -3, -4, -6]                   =>                               [0..-6]
     [-6, -4, -3, -1, 0]                   =>               [-6..-6, -4..-3, -1..0]
     [0, -1, -3, -4, -6, -7]               =>                               [0..-7]
     [-7, -6, -4, -3, -1, 0]               =>               [-7..-6, -4..-3, -1..0]
     [-1, -3, -4, -6, -7]                  =>                              [-1..-7]
     [-7, -6, -4, -3, -1]                  =>              [-7..-6, -4..-3, -1..-1]
     [-3, -4]                              =>                              [-3..-4]
     [-4, -3]                              =>                              [-4..-3]
     [-3, -4, -6, -8, -9, -10, -11, -12, - =>                             [-3..-42]
     [-42, -41, -40, -39, -38, -37, -36, - =>             [-42..-8, -6..-6, -4..-3]


     harp:~ > cat a.rb
     tests = [
       [],
       [0],
       [0,1],
       [0,1,2],
       [0,1,2,3],
       [0,3],
       [0,3,5],
       [0,3,5,7],
       [0,1,3,4],
       [0,1,3,4,6,7],
       [0,1,3,4,6,7,9,10],
       [0,1,3,4,6,7,10],
       [0,3,4,6,7,9,10],
       [0,1,3],
       [0,3,4],
       [0,-1],
       [0,-1,-2],
       [0,-1,-3,-4],
       [0,-1,-3,-4,-6],
       [0,-1,-3,-4,-6,-7],
       [-1,-3,-4,-6,-7],
       [-3,-4],
       [-3,-4,-6, *(-42 .. -8).to_a.reverse],
     ]

     def sequences d
       d.inject([d[0]..d[0]]){|r,x| r<<(((r.last.end+1>=x)?r.pop.first: x)..x)}
     end

     tests.each do |a|
       begin
         printf "%-37.37s => %37.37s\n", a.inspect, sequences(a).inspect
         a.reverse!
         printf "%-37.37s => %37.37s\n", a.inspect, sequences(a).inspect
       rescue => e
         printf "%-37.37s => %s\n", a.inspect, "#{ e } (#{ e.message })"
       end
     end


it is short though ;-)


-a
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