def helper(left: int, right: int) -> TreeNode:
if left > right:
return None
mid = (left + right) // 2
node = TreeNode(nums[mid])
node.left = helper(left, mid-1)
node.right = helper(mid+1, right)
return node
def constructFromPrePost(self, pre: List[int], post: List[int]) -> TreeNode:
root = TreeNode(pre.pop(0))
if root.val != post[0]:
root.left = self.constructFromPrePost(pre, post)
if root.val != post[0]:
root.right = self.constructFromPrePost(pre, post)
post.pop(0)
return root
def helper2(low:int, hight: int) -> TreeNode:
if low > hight:
return None
rootval = postorder.pop();
node = TreeNode(rootval)
mid = valindex[rootval];
node.right = helper2(mid+1, hight)
node.left = helper2(low, mid-1)
return node
def helper() -> TreeNode:
root = TreeNode(pre[self.preindex])
self.preindex += 1
if root.val != post[self.postindex]:
root.left = helper()
if root.val != post[self.postindex]:
root.right = helper()
self.postindex += 1
return root
def listToBST(l: int, r: int) -> TreeNode:
if l > r:
return None
if l == r:
return TreeNode(sorted_list[l])
mid = (l + r) // 2
node = TreeNode(sorted_list[mid])
node.left = listToBST(l, mid - 1)
node.right = listToBST(mid + 1, r)
return node
def helper(infrom: int, postfrom: int, length: int) -> TreeNode:
if length == 0:
return None
rootval = postorder[postfrom+length-1]
node = TreeNode(rootval)
inorderindex = valindex[rootval]
leftlen = inorderindex - infrom
rightlen = length - 1 - leftlen
node.left = helper(infrom, postfrom, leftlen)
node.right = helper(infrom+leftlen+1, postfrom+leftlen, rightlen)
return node
def deleteNode(self, root: TreeNode, key: int) -> TreeNode:
def previousNumber(node: TreeNode) -> int:
"""
previous number is the maximum of its left subtree(if not null), one left, other right
:param node:
:return:
"""
#node and node.left is not null
node = node.left
while node.right:
node = node.right
return node.val
def nextNumber(node: TreeNode) -> int:
"""
next number is the minimum of its right subtree(if not null), one right, other left
:param node:
:return:
"""
#node and node.right is not null
node = node.right
while node.left:
node = node.left
return node.val
if not root:
return root
if key < root.val:
root.left = self.deleteNode(root.left, key)
elif key > root.val:
root.right = self.deleteNode(root.right, key)
else: #key = root.val
"""
if not root.left and not root.right:
root = None
elif root.right:
root.val = nextNumber(root)
root.right = self.deleteNode(root.right, root.val)
else: #root.left
root.val = previousNumber(root)
root.left = self.deleteNode(root.left, root.val)
"""
if not root.left:
return root.right
elif not root.right:
return root.left
root.val = nextNumber(root)
root.right = self.deleteNode(root.right, root.val)
return root
def helper() -> TreeNode:
val, sign = 0, True
if s[self.index] == '-':
sign = False
self.index += 1
while self.index < len(s) and s[self.index].isdigit():
val = val * 10 + int(s[self.index])
self.index += 1
if not sign:
val = -val
node = TreeNode(val)
if self.index < len(s) and s[self.index] == '(':
self.index += 1
node.left = helper()
if self.index < len(s) and s[self.index] == '(':
self.index += 1
node.right = helper()
if self.index < len(s) and s[self.index] == ')':
self.index += 1
return node