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Andrés Ucero
Asked: 2020-01-05 17:02:30 +0800 CST 2020-01-05 17:02:30 +0800 CST

Get the value NOT repeated in the array

  • 772

I'm working with rails, it happens that when I run my project, I get to the point where I only have to have duplicate values ​​inside the arrays, therefore I have to eliminate the NOT repeated values, for example:

array=[2017,2017,2018,2018,2019]

in this case the value 2019 should be eliminated, since it is not repeated

What I have is the following:

    def saca_no_repetido(array)
        for i in 0...array.length
            if(array[i]!=array[i+1] && array[i+1]!=nil)
                array.delete_at(i)
            end
        end
        return array
    end
ruby

2 Answers

  1. Ruby has methods (via the module Enumerable) to manipulate collections; for your specific case, you can use selectand count:

    array.select { |element| array.count(element) > 1 }
#=> [2017, 2017, 2018, 2018]

    This solution is the simplest, however it is slow if you decide to apply it to large arrays; in that case, you could use the group_by, selectand flat_map:

    array.group_by(&:itself).select { |_, v| v.size > 1 }.flat_map(&:last)
#=> [2017, 2017, 2018, 2018]

    This option is less readable, but faster.

    The use of Enumerableis very common in Ruby and is what the community recommends to use (it is more idiomatic ), as opposed to the use of for, which you will find in very specific solutions (it is more common to use each).

    • 6
  2. Best Answer

    Due to the problem you express, the following array should be returned:

    [2017,2017,2018,2018] #sin el 2019

    For that I have modified a little the code that you have shared:

    #He puesto los mismos datos 
array=[2017,2017,2018,2018,2019] 


def saca_no_repetido(array)
  for i in 0...array.length
    dato = array[i] #para guardar un dato 
    encontrado = 0 #contador
    for j in 0...array.length #He puesto un nuevo for
      if(dato == array[j] && i!=j) #Si el dato es igual pero no la posición
        encontrado  += 1 
      end
    end
    if(encontrado == 0) #Nueva clausura if
      array.delete_at(i)
    end
  end
  return array
end

puts saca_no_repetido(array) #imprime el array

    Result

    2017

    2017

    2018

    2018

    Explanation

    1. I have put a fornest, this so that every time it goes through a data, it goes through the same array again in search of another data that is the same.

    2. I created a closure if, which clauses if the data of the first forcoincides with that of the second, also that the position is not the same in both, since the same data would be found and not a different one.

    3. If an equal data is found in a different position in arraythe variable encontradoincreases in 1if it is at the end is 0, it means that it is a data that is not repeated and is eliminated from the array.

    It also works if the repeated data is not next to each other:

    array=[2017,2018,2019,2018,2017]

    Result

    2017

    2018

    2018

    2017

    • 4