# inorder
def isValidBST3(self, root: TreeNode) -> bool:
stack = []
pre = None
while root or stack:
while root:
stack.append(root)
root = root.left
root = stack.pop()
if pre and root.val <= pre.val:
return False
pre = root
root = root.right
return True
if __name__ == '__main__':
root = TreeNode(1)
root.left = TreeNode(5)
a = TreeNode(4)
root.right = a
a.left = TreeNode(3)
a.right = TreeNode(6)
PrintBST.printBST(root)
solution = Solution()
result = solution.isValidBST3(root)
print('Is valid BST:{}'.format(result))
result = solution.isValidBST3(root)
print('Is valid BST:{}'.format(result))
node.left, node.right = node.right, node.left
if node.left:
stack.append(node.left)
if node.right:
stack.append(node.right)
return root
if __name__ == '__main__':
root = TreeNode(1)
b = TreeNode(2)
b.left = TreeNode(1)
b.right = TreeNode(3)
root.left = b
a = TreeNode(7)
root.right = a
a.left = TreeNode(6)
a.right = TreeNode(9)
PrintBST.printBST(root)
solution = Solution()
node = solution.invertTree(root)
PrintBST.printBST(node)
node = solution.invertTree2(root)
PrintBST.printBST(node)
from typing import List
from Tree.PrintBST import PrintBST
# Definition for a binary tree node.
class TreeNode:
def __init__(self, val=0, left=None, right=None):
self.val = val
self.left = left
self.right = right
class Solution:
def sortedArrayToBST(self, nums: List[int]) -> TreeNode:
if len(nums) == 0:
return None
mid = len(nums) // 2
return TreeNode(val=nums[mid],
left=self.sortedArrayToBST(nums[:mid]),
right=self.sortedArrayToBST(nums[mid + 1:]))
if __name__ == '__main__':
nums = [-10, -3, 0, 5, 9]
solution = Solution()
bst = solution.sortedArrayToBST(nums)
PrintBST.printBST(bst)
def generateTrees(self, n: int) -> List[TreeNode]:
ans = []
if n == 0:
return ans
def helper(start, end):
ans = []
if start > end:
ans.append(None)
return ans
for i in range(start, end + 1):
left = helper(start, i - 1)
right = helper(i + 1, end)
for node_l in left:
for node_r in right:
root = TreeNode(i)
root.left = node_l
root.right = node_r
ans.append(root)
return ans
return helper(1, n)
if __name__ == '__main__':
solution = Solution()
list_nodes = solution.generateTrees(3)
for node in list_nodes:
PrintBST.printBST(node)