Update README.md

Author: chienlun

README.md

@@ -115,7 +115,6 @@
 |404|[Sum of Left Leaves](https://leetcode.com/problems/sum-of-left-leaves/#/description)| [Python ](./tree/Yu/404_sum_of_Left_Leaves.py) | _O(N)_| _O(1)_|[:tv:](https://youtu.be/pH-KxPcBF_4)|
 |270|[Closest Binary Search Tree Value](https://leetcode.com/problems/closest-binary-search-tree-value/#/description)| [Python ](./tree/Yu/270.py)| _O(N)_| _O(1)_|[:tv:](https://youtu.be/RwvQyKJxHZk)|
 |563|[Binary Tree Tilt](https://leetcode.com/problems/binary-tree-tilt/#/description)| [Python ](./tree/Yu/563.py) | _O(N)_| _O(1)_ |[:tv:](https://youtu.be/47FQVP4ynk0)|
-|637|[Average of Levels in Binary Tree](https://leetcode.com/problems/average-of-levels-in-binary-tree/)| [Python ](./tree/Yu/637.py) | _O(N)_| _O(1)_ ||
 
 ## Tree Medium
 |  #  | Title | Solution | Time | Space | Video|
@@ -124,10 +123,11 @@
 |102|[Binary Tree Level Order Traversal](https://leetcode.com/problems/binary-tree-level-order-traversal/#/description)| [Python ](./tree/Yu/102.py) | _O(N)_| _O(N)_  |[:tv:](https://youtu.be/IWiprpdSgzg)|
 |107|[Binary Tree Level Order Traversal II](https://leetcode.com/problems/binary-tree-level-order-traversal-ii/#/description)| [Python ](./tree/Yu/107.py) | _O(N)_| _O(N)_  ||
 |515|[Find Largest Value in Each Tree Row](https://leetcode.com/problems/find-largest-value-in-each-tree-row/#/description)| [Python ](./tree/Yu/515.py) | _O(N)_| _O(1)_  ||
+|199|[Binary Tree Right Side View](https://leetcode.com/problems/binary-tree-right-side-view/#/description)| [Python ](./tree/Yu/199.py) | _O(N)_| _O(N)_  |[:tv:](https://youtu.be/_iKUgRiUYKA)|
+|637|[Average of Levels in Binary Tree](https://leetcode.com/problems/average-of-levels-in-binary-tree/)| [Python ](./tree/Yu/637.py) | _O(N)_| _O(1)_ ||
 |437|[Path Sum III](https://leetcode.com/problems/path-sum-iii/#/description)| [Python ](./tree/Yu/437.py) | _O(N^2)_| _O(1)_ | |[:tv:](https://www.youtube.com/watch?v=NTyOEYYyv-o)|
 |538|[Convert BST to Greater Tree](https://leetcode.com/problems/convert-bst-to-greater-tree/#/description)| [Python ](./tree/Yu/538.py) | _O(N)_| _O(1)_ |[:tv:](https://youtu.be/YoEPWtXmkD4)|
 |236|[Lowest Common Ancestor of a Binary Tree](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/#/description)| [Python ](./tree/Yu/236.py) | _O(N)_| _O(1)_ |[:tv:](https://youtu.be/WqNULaUhPCc)|
-|199|[Binary Tree Right Side View](https://leetcode.com/problems/binary-tree-right-side-view/#/description)| [Python ](./tree/Yu/199.py) | _O(N)_| _O(N)_  |[:tv:](https://youtu.be/_iKUgRiUYKA)|
 |114|[Flatten Binary Tree to Linked List](https://leetcode.com/problems/flatten-binary-tree-to-linked-list/#/solutions)| [Python ](./tree/Yu/114.py) | _O(N)_| _O(1)_  |[:tv:](https://youtu.be/LfKRZ_qCmYQ)|
 |230|[Kth Smallest Element in a BST](https://leetcode.com/problems/kth-smallest-element-in-a-bst/#/description)| [Python ](./tree/Yu/230.py) | _O(N)_| _O(1)_  |[:tv:](https://youtu.be/CfNRc82ighw)|
 |582|[Kill Process](https://leetcode.com/problems/kill-process/#/description)| [Python ](./tree/Yu/582.py) | _O(N)_| _O(N)_  | [:tv:](https://youtu.be/fKR1n35Sj8s)|