convert-bst-to-greater-tree.md

<p>Given a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus sum of all keys greater than the original key in BST.</p>

<p>
<b>Example:</b>
<pre>
<b>Input:</b> The root of a Binary Search Tree like this:
              5
            /   \
           2     13

<b>Output:</b> The root of a Greater Tree like this:
             18
            /   \
          20     13
</pre>
</p>