Finish Tree section of LC problems

Wahoo! I need to remember that the inorder traversal of a BST should be
sorted. This piece of trivia comes in handy for a variety of BST related
problems.

I also think being able to do a {pre,in,post}-order traversal recursively and
iteratively is a skill that I need to develop.

1 files changed, 3 insertions, 3 deletions

diff --git a/scratch/facebook/leetcode.org b/scratch/facebook/leetcode.org
index fad137f27083..00cdcd6196bb 100644
--- a/scratch/facebook/leetcode.org
+++ b/scratch/facebook/leetcode.org
@@ -140,11 +140,11 @@
    https://leetcode.com/problems/serialize-and-deserialize-binary-tree/
 ** DONE Subtree of Another Tree
    https://leetcode.com/problems/subtree-of-another-tree/
-** TODO Construct Binary Tree from Preorder and Inorder Traversal
+** DONE Construct Binary Tree from Preorder and Inorder Traversal
    https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/
-** TODO Validate Binary Search Tree
+** DONE Validate Binary Search Tree
    https://leetcode.com/problems/validate-binary-search-tree/
-** TODO Kth Smallest Element in a BST
+** DONE Kth Smallest Element in a BST
    https://leetcode.com/problems/kth-smallest-element-in-a-bst/
 ** DONE Lowest Common Ancestor of BST
    https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/