title: Data Structure: Uniqueness in lists
body: <p>i have 2 lists,one list l1 contains n1 elements and another list l2 contains n2 elements.Both lists are not the same length and contain duplicate elements.I want to create another list which has unique elements from both l1 and l2.How can i do this efficiently and what would be the performance of this solution?</p>
  
  <p>P.S :  i want a solution which does not make use of any other data structures.</p>