Example of mode implementation for Alex

example.rb

class Example

  # mode - Just another mode implementation
  #
  # @author Santiago Traversa

  # @param [Array<Integer>]

  # @example [1,1,2,3,4] #=> 1
  #
  # @raise [ExceptionClass] if param is not an Array
  #
  # @return [Integer] The most repeated integer in the initial array

  def mode(numbers)

    # Check if numbers is an Array
    unless numbers.is_a?(Array)
      raise ArgumentError.new("Only an Array is allowed")
    end

    # Check if all the values in they Array are integers
    unless numbers.all? {|i| i.is_a?(Integer) }
      raise ArgumentError.new("Only an Array with all integers inside is allowed")
    end

    summary = {}

    # Build a hash counting the times each number appears
    numbers.each do |x|
      # if summary[x]
      #   summary[x] += 1
      # else
      #   summary[x] = 1
      # end

      # Simple hack to avoid the if statement
      summary[x] = summary[x].to_i + 1
    end

    # Return the key (actually the number)
    # of the most repeated number in the array
    numbers.max_by { |times| summary[times] }
  end
end

example = Example.new

numbers = [1,2,2,3,4,5,5,99]
puts example.mode(numbers) # Returns 2

numbers = [1,2,2,3,4,4,4,5,5,99]
puts example.mode(numbers) # Returns 4

numbers = [1,2,2,3,4,4,4,5,5,5,5,99]
puts example.mode(numbers) # Returns 5

numbers = [1]
puts example.mode(numbers) # Returns 1

numbers = []
puts example.mode(numbers) # Returns nil

numbers = nil
puts example.mode(numbers) # Returns ArgumentError

numbers = [1,:two,3]
puts example.mode(numbers) # Returns ArgumentError

numbers = [1,'two',3,3]
puts example.mode(numbers) # Returns ArgumentError