title: Worst time complexity of a BST (traversing it postorder )
body: <p>Consider the time complexity of a post-order traversal on a binary search tree of <code>N</code> nodes. I know it takes <code>O(N)</code> to visit all the nodes, in the general case, but what is the complexity in the worst case, when BST is a list? I think it takes <code>O(N^2)</code>, because it will traverse <code>N</code> nodes to go reach the end, and <code>N</code> nodes to go back to the start. That means <code>N*N = N^2</code>, so I think it is <code>O(N^2)</code>. Is it right?</p>