Solve additional Tree problems

Only three more to go!

scratch/facebook/leetcode.org

@@ -132,13 +132,13 @@
    https://leetcode.com/problems/same-tree/
 ** DONE Invert/Flip Binary Tree
    https://leetcode.com/problems/invert-binary-tree/
-** TODO Binary Tree Maximum Path Sum
+** DONE Binary Tree Maximum Path Sum
    https://leetcode.com/problems/binary-tree-maximum-path-sum/
-** TODO Binary Tree Level Order Traversal
+** DONE Binary Tree Level Order Traversal
    https://leetcode.com/problems/binary-tree-level-order-traversal/
 ** DONE Serialize and Deserialize Binary Tree
    https://leetcode.com/problems/serialize-and-deserialize-binary-tree/
-** TODO Subtree of Another Tree
+** DONE Subtree of Another Tree
    https://leetcode.com/problems/subtree-of-another-tree/
 ** TODO Construct Binary Tree from Preorder and Inorder Traversal
    https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/
@@ -152,7 +152,7 @@
    https://leetcode.com/problems/implement-trie-prefix-tree/
 ** DONE Add and Search Word
    https://leetcode.com/problems/add-and-search-word-data-structure-design/
-** TODO Word Search II
+** DONE Word Search II
    https://leetcode.com/problems/word-search-ii/
 * Heap
 ** DONE Merge K Sorted Lists