delete-node-in-a-bst.md

Given a root node reference of a BST and a key, delete the node with the given key in the BST. Return the root node reference (possibly updated) of the BST.

Basically, the deletion can be divided into two stages:

1. Search for a node to remove.
2. If the node is found, delete the node.

Note: Time complexity should be O(height of tree).

Example:

root = [5,3,6,2,4,null,7]
key = 3
5

/ 

3   6
/ \   

2   4   7
Given key to delete is 3. So we find the node with value 3 and delete it.
One valid answer is [5,4,6,2,null,null,7], shown in the following BST.
5

/ 

4   6
/     

2       7
Another valid answer is [5,2,6,null,4,null,7].
5

/ 

2   6
\   

4   7