Remove Node in Binary Search Tree

Problem

Given a root of Binary Search Tree with unique value for each node. Remove the node with given value. If there is no such a node with given value in the binary search tree, do nothing. You should keep the tree still a binary search tree after removal.

Example

Given binary search tree:

    5
   / \
  3   6
 / \
2   4

Remove 3, you can either return:

    5
   / \
  2   6
   \
    4

or

    5
   / \
  4   6
 /
2