title: The AVL tree four rotate is not works
body: <p>We know for keep a binary tree balance, we can use RR LL RL LR foure rotate to make the unbalance tree to balance, But if we have a balance tree as fllows:</p>
  
  <pre><code>        885
          / \
         /   \
       659   912
       / \     \
      /   \    934
    212   759
    / \
   /   \
  11   344
  </code></pre>
  
  <p>if we add a node (168) to this tree and the tree like this:</p>
  
  <pre><code>        885
          / \
         /   \
       659   912
       / \     \
      /   \    934
    212   759
    / \
   /   \
  11   344
   \
   168
  </code></pre>
  
  <p>the tree is not balance, but I can not use any of four rotate(RR, LL ,RL, LR) to make the tree balance again. anyone TELL me why?</p>