Efficient way to remove duplicates from multiple array (array of array of string)

Question

I'm trying to figure out an efficient way to remove duplicates from an array of array of string but not within a single array, but from all array.

It's hard to explain so let me show an example:

[
  ["Word1", "Word2", "Word3", "Word4"],
  ["Word1", "Word5", "Word3", "Word4"],
  ["Word1", "Word2", "Word3", "Word7"],
]

Expected Results:

[
  ["Word2", "Word4"],
  ["Word5", "Word4"],
  ["Word2", "Word7"],
]

Index 0: Removed because all Index 0 are identicals.

Index 1: Kept because not all Index 1 are identicals. and so on...

The closer I could come up is

def clean_duplicates(attributes)
    valid_attributes = attributes.map { [] }

    attributes.first.count.times.each do |i|
        next if attributes.all? { |v_attrs| v_attrs[i] == attributes.last[i] }

        attributes.each_with_index do |_, v|
            valid_attributes[v].push(attributes[v][i])
        end
    end

    valid_attributes
end

clean_attributes([["Word1", "Word2", "Word3", "Word4"], ["Word1", "Word5", "Word3", "Word4"], ["Word1", "Word2", "Word3", "Word7"]])

=> [["Word2", "Word4"], ["Word5", "Word4"], ["Word2", "Word7"]]

Is there a better way?

Thank you!

nPn · Accepted Answer · 2021-12-21 14:02:50Z

4

Here is a solution using Array#transpose and Array#select

    [["Word1", "Word2", "Word3", "Word4"], ["Word1", "Word5", "Word3", "Word4"], ["Word1", "Word2", "Word3", "Word7"]]
.transpose
.select {|i| i.uniq.size > 1}
.transpose

First step is to transpose the input to get the following:

[["Word1", "Word1", "Word1"], ["Word2", "Word5", "Word2"], ["Word3", "Word3", "Word3"], ["Word4", "Word4", "Word7"]]

Then you only want to keep the elements that are not all the same.

select { |i| i.uniq.size > 1 }

will select only those elements that are not all the same value, giving you:

[["Word2", "Word5", "Word2"], ["Word4", "Word4", "Word7"]]

finally you transpose that into your desired result.

transpose
[["Word2", "Word4"], ["Word5", "Word4"], ["Word2", "Word7"]]

edited Dec 21, 2021 at 14:02

answered Dec 21, 2021 at 13:53

nPn

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1 Comment

Jamesst20 Over a year ago

I had never seen transpose before ! Smart and elegant ! Thank you!

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