From: "Jan E." <lists@...>
Date: 2012-07-25T16:01:11+09:00
Subject: Re: Help with exercise from Chris Pine's Ruby Book: Sort without using .sort

Your method is of course correct. But you don't really use the 
recursion, since you basically just replaced the while loop with a 
method repeatedly calling itself.

You might want to reduce the problem to a smaller task first. For 
example, you could write a method that finds the minimum of an array and 
returns both the minimum and the rest of the array. You can then use 
this simple method to recursively build a sorted array:

#-----------------------
def find_min array
  min, rest =
    array.first, []
  array.drop(1).each do |element|
    if element < min
      rest << min
      min = element
    else
      rest << element
    end
  end
  return min, rest
end

def min_sort array
  return array if array.empty?
  min, rest =
    find_min array
  [min] + min_sort(rest)
end
#-----------------------

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