From: Kevin Compton <klcompt@...>
Date: 2007-05-11T14:28:48+09:00
Subject: Re: how to remove dups from 2 lists?

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I'm also not real sure of what exactly you wanted but..
I assumed the following :


def remove_dups_from_both_lists (list1, list2)
  list1_dup = list1.dup
  remove_dups_from_first_list list1, list2
  remove_dups_from_first_list list2, list1_dup
end

def remove_dups_from_first_list(list_to_prune, list_with_dups)
  hash_with_occurrence_count = get_hash_with_occurrence_count list_to_prune
  decrement_count_for_dups(list_with_dups, hash_with_occurrence_count)
  get_remaining_item_list(list_to_prune, hash_with_occurrence_count)
end

def get_hash_with_occurrence_count(list)
  hsh = Hash.new { |h,k| h[k] = 0}
  list.each { |item| hsh[item] += 1 }
  hsh
end

def decrement_count_for_dups(list, other_list_as_hash)
  list.each { |item| other_list_as_hash[item] -= 1 }
end

def get_remaining_item_list(list, list_as_hash)
  list.each_with_index do |item, idx|
    if (list_as_hash[item] > 0)
      list_as_hash[item] -= 1
    else
      list[idx] = nil
    end
  end
  list.compact
end

list1 = %w{one one two three four four five}
list2 = %w{one three three four five five five}
puts "before --- list1:#{list1}"
puts "before --- list2:#{list2}"
remove_dups_from_both_lists list1, list2
puts "after --- list1:#{list1}"
puts "after --- list2:#{list2}"



On 5/10/07, Mike Steiner <mikejaysteiner@gmail.com> wrote:
>
> I'm trying to write some code that removes all elements from 2 lists that
> are in both lists. However, I don't want any duplicates from each list
> deleted also (which is what the array "-" operator does). The code I have
> now doesn't handle restarting the current iteration for both loops when a
> match is found and deleted in both loops. Here's the code:
>
> def RemoveDupsFromLists ( list1 , list2 )
>     list1.each_index do | i |
>         list2.each_index do | j |
>             if list1[i] == list2[j]
>                 list1.delete_at ( i )
>                 list2.delete_at ( j )
>             end
>         end
>     end
>     return [ list1 , list2 ]
> end
>
> What's weird is that doing this is easy in C (my first language), but
> difficult in Ruby. Everything else I've seen has been MUCH easier in Ruby.
>
> Mike Steiner
>

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