Advance Tree Algorithm 1 Summary - Leetcode

1. Serialization

[Method 1] pre-order+in-order or in-order+post-order
[Problem] same nodes will cause problems in deserialization.
e.g., pre-oder = [5,5,5,5], in-order = [5,5,5,5] ->no way to figure out what exactly the tree looks like.

[Method 2] level-order serialization
    

[1,2,3,4,null,5,6,null,null,null,null]

(You can also trim all the "null" in the end)

    

2. Binary Search Tree 

1. Predecessor and Successor

java.util.TreeMap support API ceiling(value) and floor(value)
[Question]
270. Closest Binary Search Tree Value

2. other BST questions

222. Count Complete Tree Nodes
230. Kth Smallest Element in a BST