# Definition for a binary tree node.

# class TreeNode(object):

# def __init__(self, x):

# self.val = x

# self.left = None

# self.right = None

class Solution(object):

def trimBST(self, root, L, R):

"""

:type root: TreeNode

:type L: int

:type R: int

:rtype: TreeNode

"""

# Each subtree visited we move through, each subtree's root will be node

def trim(node):

# Reaching the depth of a BST

if not node:

return None

# Range should be within L - R, hence if node is less than L, trim the right

elif node.val < L:

return trim(node.right)

# Range should be within L - R, hence if node is greater than R, trim the left

elif node.val > R:

return trim(node.left)

# Else, trim both the sides

else:

node.left = trim(node.left)

node.right = trim(node.right)

return node

return trim(root)