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.
3
/ \
0 4
\
2
/
1
L = 1
R = 3
Output:
3
/
2
/
1
解法：好像没什么说的，递归
# 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
"""
if not root:
return None
if root.val < L:
return self.trimBST(root.right,L,R)
elif root.val >R:
return self.trimBST(root.left,L,R)
else:
root.left = self.trimBST(root.left,L,R)
root.right = self.trimBST(root.right,L,R)
return root
