From: Mike Steiner <mikejaysteiner@...>
Date: 2007-05-12T08:11:37+09:00
Subject: Re: how to remove dups from 2 lists?

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Good idea about the & operator for sets, but there could be more than 1
group of matches, so I'd have to iterate:

a =3D [ 1, 1, 2, 3, 4, 4, 4, 5 ]
b =3D [ 1, 2, 2, 4, 4, 6, 7 ]
results =3D a & b
while results
    results.each do | m |
        a =3D a - m
        b =3D b - m
    end
    results =3D a & b
end

I think this will work, and it's sort of elegant (well, not as elegant as
having it built into Ruby already :-)).

Mike Steiner

On 5/11/07, Wolfgang N=E1dasi-Donner <wonado@donnerweb.de> wrote:
>
> > On May 10, 2007, at 10:18 PM, Mike Steiner wrote:
> >
> >> I'm trying to write some code that removes all elements from 2 lists
> that
> >> are in both lists. However, I don't want any duplicates from each list
> >> deleted also (which is what the array "-" operator does). The code I
> have
> >> now doesn't handle restarting the current iteration for both loops whe=
n
> a
> >> match is found and deleted in both loops. Here's the code:
> >>
> >> def RemoveDupsFromLists ( list1 , list2 )
> >>    list1.each_index do | i |
> >>        list2.each_index do | j |
> >>            if list1[i] =3D=3D list2[j]
> >>                list1.delete_at ( i )
> >>                list2.delete_at ( j )
> >>            end
> >>        end
> >>    end
> >>    return [ list1 , list2 ]
> >> end
> >>
> >> What's weird is that doing this is easy in C (my first language), but
> >> difficult in Ruby. Everything else I've seen has been MUCH easier in
> >> Ruby.
> >>
> >> Mike Steiner
>
> Isn't this what you want?
>
> irb(main):001:0> a =3D %w{a b c d e f g a b c}
> =3D> ["a", "b", "c", "d", "e", "f", "g", "a", "b", "c"]
> irb(main):002:0> b =3D %w{e f g h i j k h i j}
> =3D> ["e", "f", "g", "h", "i", "j", "k", "h", "i", "j"]
> irb(main):003:0> a - (a & b)
> =3D> ["a", "b", "c", "d", "a", "b", "c"]
> irb(main):004:0> b - (a & b)
> =3D> ["h", "i", "j", "k", "h", "i", "j"]
>
> Wolfgang N=E1dasi-Donner
>
>

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