```Hi,

these is my solution.
In order to solve the problem I've proceed like that:
-Start to compute all permutations possibles of emails addresses
-Remove all of them where there is a couple of persons in the same family.
-Return, randomly, one of the permutations.

Example:
\$ ./santa.rb < friends
<luke / theforce.net> -> <gus / weareallfruit.net>
<leia / therebellion.org> -> <virgil / rigworkersunion.org>
<toula / manhunter.org> -> <bruce / imbatman.com>
<gus / weareallfruit.net> -> <lindsey / iseealiens.net>
<bruce / imbatman.com> -> <leia / therebellion.org>
<virgil / rigworkersunion.org> -> <toula / manhunter.org>
<lindsey / iseealiens.net> -> <luke / theforce.net>

This is the script:

#!/usr/bin/ruby

class Friends
def initialize
@email = Hash.new
@members=0
@nb = []
end
@email[mail] = family_name
@nb[@members] = mail
@members += 1
end
end
# compute all permutation in a list
def permute(items, perms=[], res=[])
unless items.length > 0
res << perms
else
for i in items
newitems = items.dup
newperms = perms.dup
newperms.unshift(newitems.delete(i))
permute(newitems, newperms,res)
end
end
return res
end

friends = Friends.new
while line = gets
end
perms = permute(friends.email.keys)
perms.reject!{|tab|
res = false
for i in 0..tab.length-1
if friends.email[tab[i]] == friends.email[friends.nb[i]]
# same family
res = true
end
end
res
}
res = perms[rand(perms.length)]
for i in 0..res.length-1
puts "#{friends.nb[i]} -> #{res[i]}"
end

```