DouKaku?

def kujibiki(users, m)
	raise ArgumentError unless users.size >= m 

	results=[]
	m.times{
		v=((users.size * rand()).to_i)
		results << users.delete_at(v)
	}
	results
end

users = [0,1,2,3,4,5,6,7,8,9]
p kujibiki(users, 10)