1

The object of my coding exercise is to get rid of duplicates in an array without using the uniq method. Here is my code:

numbers = [1, 4, 2, 4, 3, 1, 5]

def my_uniq(array)
  sorted = array.sort
  count = 1
  while count <= sorted.length
    while true
      sorted.delete_if {|i| i = i + count}
      count += 1
    end
  end
  return sorted
end
  • When I run this, I get an infinite loop. What is wrong?
  • Can I use delete the way that I am doing with count?
  • How will it execute? Will count continue until the end of the array before the method iterates to the next index?
  • I did this with each or map, and got the same results. What is the best way to do this using each, delete_if, map, or a while loop (with a second loop that compares against the first one)?
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5
  • 2
    I'm not sure why you have 2 while loops. The inner loop is what is infinite, because while count <= sorted.length never gets looked at. Commented Mar 5, 2015 at 22:30
  • Your question has been answered. Here's another way: numbers.each_with_object({}) { |n,h| h.update(n=>:anything) }.keys #=>[1, 4, 2, 3, 5] . This requires Ruby v1.9+, which keeps hash keys in insertion order. It relies on the fact that hashes have unique keys. Commented Mar 5, 2015 at 22:39
  • Thank you for your edit Cary. I am new to SO and am learning the "proper" ways to ask questions. I will try to keep my wording to a minimum ;) and thank you for your answer as well. Commented Mar 5, 2015 at 22:56
  • Your approach is not the best because the array is changing in size, but you keep incrementing the index count. Also, the block in sorted.delete_if {|i| i = i + count} refers to indexes, but you to compare values. Commented Mar 5, 2015 at 23:03
  • That exactly answers some of the concerns I had, but was unsure of! (I am also aware that '=' should be '=='). Thanks Cary! Commented Mar 5, 2015 at 23:44

6 Answers 6

Reset to default
4

Here is a clearly written example.

numbers = [1, 4, 2, 4, 3, 1, 5]

def remove_duplicates(array)
  response = Array.new
  array.each do |number|
     response << number unless response.include?(number)
  end
  return response
end

remove_duplicates(numbers)
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1 Comment

I love this answer as well because it is along the lines of one of my many attempts...except it actually works! at least I know my thought process was correct. Again, I would love to upvote this but I don't have the rep yet. Thanks for your input jBeas, it is very easy to see what is happening and another great example to learn from :)
2

As others pointed out, your inner loop is infinite. Here's a concise solution with no loops:

numbers.group_by{|n| n}.keys

You can sort it if you want, but this solution doesn't require it.

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1 Comment

Thank you Mark! That is elegant! I don't have the rep yet (I'm a noob) to upvote your addition, or I would ;)
1

the problem is that the inner loop is an infinite loop:

while true
  sorted.delete_if {|i| i = i + count}
  count += 1
end #while

you can probably do what you are doing but it's not eliminating duplicates.

one way to do this would be:

numbers = [1, 4, 2, 4, 3, 1, 5]
target = []
numbers.each {|x| target << x unless target.include?(x) }
puts target.inspect

to add it to the array class:

class ::Array
    def my_uniq
       target = []
       self.each {|x| target << x unless target.include?(x) }
       target
    end
end

now you can do:

numbers = [1, 4, 2, 4, 3, 1, 5]
numbers.my_uniq
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6 Comments

Thank you so much Mircea!!! Since i set my count to only go as far as array.length, why is it an infinite loop? is it the placement of the count iterator? I am playing with your solution now (which is easy to understand - much appreciated for that), as it needs to be a method, and it also needs to be added to the Array Class.
nope. it's the while true. that means execute while true is true which is forever
What I have done to it is this: numbers = [1, 4, 2, 4, 3, 1, 5] def my_uniq (array) target = [] array.each {|x| target << x unless target.include?(x) } end puts target.inspect but I get "undefined local variable or method 'target for main:Object ....so I am working on that! But again, thanks!!!
ahhhhhh! the while true! I am going to go back and try to make that work, just for sh!ts and giggles :)
updated to show how you would add your own method to the array class :)
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1

You count use Set that acts like an array with does not allow duplicates:

require 'set'
numbers = [1, 4, 2, 4, 3, 1, 5]

Set.new(numbers).to_a
#=> [1, 4, 2, 3, 5]
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2 Comments

@seinna you mean "I haven't heard of the Set class yet."
oops! true indeed jBeas
1

Try using Array#& passing the array itself as parameter:

x = [1,2,3,3,3]
x & x #=> [1,2,3]
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0

This is one of the answer. However, I do not know how much of performance issue it takes to return unique

def my_uniq(ints)
    i = 0
    uniq = []

    while i < ints.length
        ints.each do |integers|
            if integers == i
                uniq.push(integers)
            end
            i += 1
        end
    end
    return uniq

end
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