def constructFromPrePost(self, pre: List[int],
post: List[int]) -> TreeNode:
'''
[1, 2, 3, 4, 5, 6, 7]
1
2 3
4 5 6 7
preorder: [1] + [2,4,5] + [3,6,7]
postorder: [4,5,2] + [6,7,3] + [1]
for each brunch, root is at the first node in preorder and last node in postorder
if we know the root value from the preorder of the left branch,
we go to the postorder and find the index of the root of the left branch
we can know the length L of the left brunch
so the left sub tree is pre[1:L+1], post[0:L]
right sub tree is pre[L+1:], post[L:-1]
we can use recursion to build the tree
'''
if not pre:
return None
root = TreeNode(pre[0])
if len(pre) == 1:
return root
L = post.index(pre[1]) + 1 # length of left branch
root.left = self.constructFromPrePost(pre[1:1 + L], post[:L])
root.right = self.constructFromPrePost(pre[1 + L:], post[L:-1])
return root
def test_testCase(self):
for Sol in [Solution1()]:
func = Sol.distanceK
root = TreeNode(3)
target = TreeNode(5)
root.left = target
root.right = TreeNode(1)
root.right.left = TreeNode(0)
root.right.right = TreeNode(8)
target.left = TreeNode(6)
target.right = TreeNode(2)
target.right.left = TreeNode(7)
target.right.right = TreeNode(4)
self.assertEqual(func(root, target, 2), [7,4,1])
def test():
root1 = TreeNode(1)
root2 = TreeNode(1)
root1.left = TreeNode(2)
root1.right = TreeNode(3)
root1.left.left = TreeNode(4)
root1.left.right = TreeNode(5)
root2.left = TreeNode(2)
root2.right = TreeNode(3)
root2.left.left = TreeNode(4)
root2.left.right = TreeNode(5)
if identical_trees(root1, root2):
print("Both trees are identical")
else:
print("Trees are not identical")
def insertIntoBST(self, root: TreeNode, val: int) -> TreeNode:
if not root:
return TreeNode(val, None, None)
if val > root.val:
root.right = self.insertIntoBST(root.right, val)
else:
root.left = self.insertIntoBST(root.left, val)
return root
def helper(nums, left, right):
if left > right:
return None
mid = (left + right) // 2
root = TreeNode(nums[mid])
if left == right:
return root
root.left = helper(nums, left, mid - 1)
root.right = helper(nums, mid + 1, right)
return root
def buildTreeUtils(self, preorder: List[int]) -> TreeNode:
if not preorder:
return None
root = TreeNode(val=preorder[0])
index = -1
for i in range(1, len(preorder)):
if preorder[i] > preorder[0]:
index = i
break
if index == -1:
root.left = self.buildTreeUtils(preorder[1:])
else:
root.left = self.buildTreeUtils(preorder[1:index])
root.right = self.buildTreeUtils(preorder[index:])
return root
succ = None
curr = root
while curr.val != key:
if curr.val > key and curr.left:
succ = curr
curr = curr.left
elif curr.right:
curr = curr.right
if curr and curr.right:
succ = find_min(curr.right)
return succ.val
if __name__ == "__main__":
root = TreeNode(9)
root.left = TreeNode(2)
root.right = TreeNode(10)
root.left.left = TreeNode(1)
root.left.right = TreeNode(7)
root.left.right.left = TreeNode(6)
root.left.right.right = TreeNode(8)
root.left.right.left.left = TreeNode(5)
# inorder(root)
# print
# print(inorder_predecessor(root, 7))
# print
print(inorder_successor_bst(root, 9))