Trim a Binary Search Tree

LeetCode Q 669- Trim a Binary Search Tree

Given a binary search tree and the lowest and highest boundaries as L and R, trim the tree so that all its elements lies in [L, R] (R >= L). You might need to change the root of the tree, so the result should return the new root of the trimmed binary search tree.

Solution:

Code:

public TreeNode trimBST(TreeNode root, int L, int R) {
  if (root == null) return root;

  if (root.val < L) return trimBST(root.right, L, R);
  if (root.val > R) return trimBST(root.left, L, R);

  root.left = trimBST(root.left, L, R);
  root.right = trimBST(root.right, L, R);

  return root;
}