title: how to combine two red black tree efficiently
body: <blockquote>
    <p>Two left-leaning red-black trees, T1 and T2, with n<sub>1</sub> entries in T1, n<sub>2</sub> entries in T2, all the entries in the T1 are less than entries in T2, find a way to combine these two trees with O(log n1 + log n2) complexity.</p>
  </blockquote>
  
  <p>Any one have any idea, totally no clue.</p>