CODEWITHSUNDEEP
ruby
Nathan
Nathan

Reputation: 402

Finding all duplicates of a Ruby Array

I am looking for an efficient way to give all the duplicate values for an array.

Example:

a = [1,2,2,3,4,7,4,4]
dups(a)

#[[2,2],[4,4,4]]

I've tried using brute force it by doing:

def dups(array)
  dups = []
  array.uniq.each do |i|
    found = array.select{|s| s.eql?(i)} 
    dups = dups.push found if found.size > 1
  end
  return dups
end

But it is pretty slow if you small percent of duplicate, since you are looping through the entire array.

Upvotes: 1

Views: 289

Answers (1)

Nathan
Nathan

Reputation: 402

def dup_group_by(array)
  array.group_by(&:itself).filter_map { |_,v| v if v.size > 1 }
end

The key was group_by method which was in the Enumerable module, I was only looking in the Array class.

Upvotes: 3

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