removing duplicates in array of arrays in Ruby

Question

I have an array of arrays, like this:

aa = [ [a,d], [a,d1], [a,d], [b,d], [b,d2], [b,d3], [b,d2], [a,d2] ]

I would like to have a unique array of arrays, not just on the first element - which I can do by doing something like aa.uniq(&:first) - but rather remove the inner arrays if BOTH values match. So the result would be:

aa = [ [a,d], [a,d1], [a,d2], [b,d], [b,d2], [b,d3] ]

Can anyone assist in pointing me to an efficient way of doing this? I have large nr of arrays - in the order of 1 million - that I need to process.

Any help appreciated! John

what do you mean by aa.uniq(&:first)?

Arup Rakshit
– Arup Rakshit

2013-05-10 09:00:11 +00:00
Commented May 10, 2013 at 9:00 — Arup Rakshit
– Arup Rakshit, Commented May 10, 2013 at 9:00

toch · Accepted Answer · 2013-05-10 07:13:46Z

2

If you need to maintain a collection of elements where each element is unique and their order is not important. You should use a Set. For instance,

require 'set'
my_set = Set.new
my_set << [1, 'a']
my_set << [1, 'a']
my_set << [1, 'b']
my_set.each { |elem| puts "#{elem}" }

It will give you

[1, "a"]
[1, "b"]

If the order is important, then use the uniq! on you array

aa.uniq!

answered May 10, 2013 at 7:13

toch

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Comments

Stephen Rauch · Accepted Answer · 2017-09-24 02:40:12Z

0

If you want to get unique elements from an array, which will remove duplicate element, you can try this:

a = [[1, 2], [2, 3], [1, 2], [2, 3], [3, 4]]
a & a #=> [[1, 2], [2, 3], [3, 4]]

edited Sep 24, 2017 at 2:40

Stephen Rauch♦

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answered Sep 24, 2017 at 2:18

IvanHuang

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Comments

Cody Gray · Accepted Answer · 2017-09-24 13:26:46Z

0

Try like this:

aa = [ ["a","d"], ["a","d1"], ["a","d"], ["b","d"] ]
aa.uniq
aa=[["a", "d"], ["a", "d1"], ["b", "d"]]

You missed double quotations ("). Inside of array, variables a, d, a, d1, etc. are strings. So, you should put them inside of double quotations ("").

edited Sep 24, 2017 at 13:26

Cody Gray♦

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answered May 10, 2013 at 7:16

visnu

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