From: Harry Kakueki <list.push@...>
Date: 2009-09-27T00:42:58+09:00
Subject: Re: How to remove duplicate elements in a 2D array

On Sat, Sep 26, 2009 at 12:34 AM, Li Chen <chen_li3@yahoo.com> wrote:
> Hi all,
>
> I have a 2D array as follow:
>
> arr=[
>
>     [ 'a',1,2,3],
>     ['b',4,5,6],
>     ['c',3,2,1],
>     ['a',1.3,2.2,3,3],
>     ...
>     ['a', 2,1,3],
>   ...
>   ['a',2.1,1.5,3]
>
> ]
>
> As you can see there are several rows containing  element 'a',
> and the last row containing 'a'' is the lastest one.  I wonder if it
> is possible to return a new array which contains the latest row having
> 'a' ,
> together with other rows.
>
>
> Thanks,
>
> Li
> --
> Posted via http://www.ruby-forum.com/.
>
>

Here is another way.
It works with Ruby 1.8.6.


p arr.map{|x| x[0]}.uniq.map{|y| arr.reverse.detect{|z| z[0] == y}}

# OR if order is important,
#

p arr.reverse.map{|x| x[0]}.uniq.reverse.map{|y|
arr.reverse.detect{|z| z[0] == y}}


Harry

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