Marking completions.

README.md

@@ -469,7 +469,7 @@ Then test it out on a computer to make sure it's not buggy from syntax.
             2-3 trees have faster inserts at the expense of slower searches (since height is more compared to AVL trees).
         You would use 2-3 tree very rarely because its implementation involves different types of nodes. Instead, people use Red Black trees.
         - [x] 23-Tree Intuition and Definition: https://www.youtube.com/watch?v=C3SsdUqasD4&list=PLA5Lqm4uh9Bbq-E0ZnqTIa8LRaL77ica6&index=2
-        - [ ] Binary View of 23-Tree: https://www.youtube.com/watch?v=iYvBtGKsqSg&index=3&list=PLA5Lqm4uh9Bbq-E0ZnqTIa8LRaL77ica6
+        - [x] Binary View of 23-Tree: https://www.youtube.com/watch?v=iYvBtGKsqSg&index=3&list=PLA5Lqm4uh9Bbq-E0ZnqTIa8LRaL77ica6
         - [x] 2-3 Trees (student recitation): https://www.youtube.com/watch?v=TOb1tuEZ2X4&index=5&list=PLUl4u3cNGP6317WaSNfmCvGym2ucw3oGp
 
     - [x] **2-3-4 Trees (aka 2-4 trees)**
@@ -479,8 +479,8 @@ Then test it out on a computer to make sure it's not buggy from syntax.
             important tool for understanding the logic behind red–black trees, and this is why many introductory algorithm texts introduce
             2-4 trees just before red–black trees, even though **2-4 trees are not often used in practice**.
         - [x] CS 61B Lecture 26: Balanced Search Trees: https://www.youtube.com/watch?v=zqrqYXkth6Q&index=26&list=PL4BBB74C7D2A1049C
-        - [ ] Bottom Up 234-Trees: https://www.youtube.com/watch?v=DQdMYevEyE4&index=4&list=PLA5Lqm4uh9Bbq-E0ZnqTIa8LRaL77ica6
-        - [ ] Top Down 234-Trees: https://www.youtube.com/watch?v=2679VQ26Fp4&list=PLA5Lqm4uh9Bbq-E0ZnqTIa8LRaL77ica6&index=5
+        - [x] Bottom Up 234-Trees: https://www.youtube.com/watch?v=DQdMYevEyE4&index=4&list=PLA5Lqm4uh9Bbq-E0ZnqTIa8LRaL77ica6
+        - [x] Top Down 234-Trees: https://www.youtube.com/watch?v=2679VQ26Fp4&list=PLA5Lqm4uh9Bbq-E0ZnqTIa8LRaL77ica6&index=5
 
     - [ ] **Red/black trees**
         - In practice: