From: "Thairuby ->a, b {a + b}" <kabkab@...>
Date: 2009-09-26T19:18:54+09:00
Subject: Re: How to  remove duplicate elements in a 2D array

The main idea is to use Hash and use the first letter ("a","b","c") as a 
key. I do it with "inject" and David do it with "Hash[]"

I change your arr

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]]

to a hash

hash={'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]}

You can see that key "a" does repeat 4 times in hash. So, the last one 
will replace the first one automatically.

finally,

hash = {"a"=>[2.1, 1.5, 3], "b"=>[4, 5, 6], "c"=>[3, 2, 1]}

The method ".map(&:flatten)" is use to converse hash back to array.
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