def convert(left, right):
if left > right: return None
mid = (left + right) // 2
node = TreeNode(nums[mid])
node.left = convert(left, mid - 1)
node.right = convert(mid + 1, right)
return node
def bst_2(cls, negtive=True):
if negtive:
root = TreeNode(0)
root.right = TreeNode(-1)
else:
root = TreeNode(1)
root.right = TreeNode(3)
root.right.left = TreeNode(2)
return root
def bst_1(cls, negtive=True):
"""
2
/ \
1 3
"""
if negtive:
root = TreeNode(2)
root.left = TreeNode(1)
root.right = TreeNode(3)
else:
root = TreeNode(1)
root.left = TreeNode(1)
return root
def insert(self, root, val):
if not root: return TreeNode(val)
if val <= root.val:
root.left = self.insert(root.left, val)
else:
root.right = self.insert(root.right, val)
return root
def bst_99(cls, correct=False):
"""
1
/
3
\
2
"""
if correct:
root = TreeNode(3)
root.left = TreeNode(1)
root.left.right = TreeNode(2)
else:
root = TreeNode(1)
root.left = TreeNode(3)
root.left.right = TreeNode(2)
return root
def insertIntoBST(self, root, val):
"""
:type root: TreeNode
:type val: int
:rtype: TreeNode
"""
if not root: return TreeNode(val)
if root.val < val:
root.right = self.insertIntoBST(root.right, val)
else:
root.left = self.insertIntoBST(root.left, val)
return root
def bst_230(cls):
"""
3
/ \
1 4
\
2
"""
root = TreeNode(3)
root.left = TreeNode(1)
root.right = TreeNode(4)
root.left.right = TreeNode(2)
return root
def recoverTree_DFS(self, root):
def inorder(node):
if not node: return
inorder(node.left)
if self.pre.val > node.val:
if not self.first:
self.first = self.pre # 记录第一次出错处, 记录较大值,
self.second = node # 记录较小值, 如果当前结点不是最终swap出错处, 则会更新结束
self.pre = node # 更新当前极小值结点, 目的是找到最终swap结点
inorder(node.right)
self.pre = TreeNode(-sys.maxsize - 1)
self.first, self.second = None, None
inorder(root)
self.first.val, self.second.val = self.second.val, self.first.val
def bst_501(cls, extend=False):
""" 4、3 都可切成 5
4
/ \
2 6
/ \ / \
1 3 5 6
"""
if not extend:
root = TreeNode(1)
root.right = TreeNode(2)
root.right.left = TreeNode(2)
return root
else:
root = TreeNode(5)
root.left, root.right = TreeNode(2), TreeNode(6)
root.left.left, root.left.right = TreeNode(1), TreeNode(3)
root.right.left, root.right.right = TreeNode(5), TreeNode(6)
return root