Added tree videos.

plan.txt

@@ -342,25 +342,35 @@ Notes:
     - traversal
     - manipulation algorithms
     - BFS (breadth-first search)
+        - MIT: https://www.youtube.com/watch?v=s-CYnVz-uh4&list=PLUl4u3cNGP61Oq3tWYp6V_F-5jb5L2iHb&index=13
+        - level order (BFS, using queue)
+            time complexity: O(n)
+            space complexity: best: O(1), worst: O(n/2)=O(n)
     - DFS (depth-first search)
-    - know the difference between these:
+        - MIT: https://www.youtube.com/watch?v=AfSk24UTFS8&list=PLUl4u3cNGP61Oq3tWYp6V_F-5jb5L2iHb&index=14
+        - notes:
+            time complexity: O(n)
+            space complexity:
+                best: O(log n) - avg. height of tree
+                worst: O(n)
         - inorder (DFS: left, self, right)
         - postorder (DFS: left, right, self)
         - preorder (DFS: self, left, right)
-        - level order (BFS, using queue)
+
 
 - Binary search trees: BSTs
     * - Series: https://www.coursera.org/learn/data-structures-optimizing-performance/lecture/p82sw/core-introduction-to-binary-search-trees
     * - Series: https://class.coursera.org/algs4partI-010/lecture/43
         - starts with symbol table and goes through BST applications
     * - https://www.coursera.org/learn/data-structures/lecture/E7cXP/introduction
+    - MIT: https://www.youtube.com/watch?v=9Jry5-82I68
     - C/C++:
         * - https://www.youtube.com/watch?v=COZK7NATh4k&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P&index=28
         * - https://www.youtube.com/watch?v=hWokyBoo0aI&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P&index=29
         * - https://www.youtube.com/watch?v=Ut90klNN264&index=30&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P
-        - https://www.youtube.com/watch?v=_pnqMz5nrRs&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P&index=31
-        - https://www.youtube.com/watch?v=9RHO6jU--GU&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P&index=32
-        - https://www.youtube.com/watch?v=86g8jAQug04&index=33&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P
+        * - https://www.youtube.com/watch?v=_pnqMz5nrRs&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P&index=31
+        * - https://www.youtube.com/watch?v=9RHO6jU--GU&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P&index=32
+        * - https://www.youtube.com/watch?v=86g8jAQug04&index=33&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P
         - https://www.youtube.com/watch?v=gm8DUJJhmY4&index=34&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P
         - https://www.youtube.com/watch?v=yEwSGhSsT0U&index=35&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P
         - https://www.youtube.com/watch?v=gcULXE7ViZw&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P&index=36
@@ -372,6 +382,7 @@ Know least one type of balanced binary tree (and know how it's implemented):
     - splay trees
         - https://www.coursera.org/learn/data-structures/lecture/O9nZ6/splay-trees
     - AVL trees
+        - MIT: https://www.youtube.com/watch?v=FNeL18KsWPc&list=PLUl4u3cNGP61Oq3tWYp6V_F-5jb5L2iHb&index=6
         - https://www.coursera.org/learn/data-structures/lecture/Qq5E0/avl-trees
         - https://www.coursera.org/learn/data-structures/lecture/PKEBC/avl-tree-implementation
         - https://www.coursera.org/learn/data-structures/lecture/22BgE/split-and-merge