title: Binary Tree with negative values
body: <p>I was solving a data structure problem and I came across a Binary Tree problem: </p>
  
  <p>Find the maximum node in a binary tree, return the node.
  Given the following BST</p>
  
  <pre><code>    1
     /   \
   -5     2
   / \   /  \
  0   3 -4  -5 
  </code></pre>
  
  <p>I thought that in a Binary Tree, every node's key is greater than all keys in its left sub-tree, and less than all keys in its right sub-tree. </p>
  
  <p>Can a Binary Tree be unsorted ? </p>