title: Do I misunderstand the meaning of exercise 2.65 of SICP?
body: <p>Here is the exercise 2.65 of SICP:</p>
  
  <blockquote>
    <p>Use the results of exercises 2.63 and 2.64 to give Θ(n) implementations of union-set and intersection-set for sets implemented as (balanced) binary trees.</p>
  </blockquote>
  
  <p>In the chapter "Sets as ordered lists" and exercise 2.62, we already have the union-set and intersection-set for the ordered lists. I have searched the Internet, the answer of 2.65 is too simple to accept, they just convert the binary trees into lists and still use the the union-set and intersection-set for the ordered lists.</p>
  
  <p>In my opinion, we need to convert the sets into binary trees and rewrite the union-set and intersection-set for the binary trees. </p>
  
  <p>So, do I misunderstand the meaning of exercise 2.65 of SICP? Or is there a good answer?</p>