def test_binary_tree_paths(self):
node1 = TreeNode(1)
node2 = TreeNode(2)
node3 = TreeNode(3)
node5 = TreeNode(5)
node1.left = node2
node1.right = node3
node2.right = node5
s = Solution()
res = s.binaryTreePaths(node1)
self.assertEqual(["1->2->5", "1->3"], res)
def test_is_valid_bst2(self):
s = Solution()
node1 = TreeNode(1)
node2 = TreeNode(2)
node3 = TreeNode(3)
node4 = TreeNode(4)
node5 = TreeNode(5)
node6 = TreeNode(6)
node5.left = node1
node5.right = node4
node4.left = node3
node4.right = node6
self.assertFalse(s.isValidBST(node5))
def flatten(self, root: TreeNode) -> None:
"""
Do not return anything, modify root in-place instead.
"""
if not root:
return
self.flatten(root.left)
self.flatten(root.right)
tmp = root.right
root.right = root.left
root.left = None
while root.right:
root = root.right
root.right = tmp
def test_is_valid_bst(self):
s = Solution()
node1 = TreeNode(1)
node2 = TreeNode(2)
node3 = TreeNode(3)
node2.left = node1
node2.right = node3
self.assertTrue(s.isValidBST(node2))
def test_is_balanced(self):
s = Solution()
node1 = TreeNode(1)
node2 = TreeNode(2)
node3 = TreeNode(3)
node2.left = node1
node2.right = node3
self.assertTrue(s.isBalanced(node2))
def sortedArrayToBST(self, nums: List[int]) -> Optional[TreeNode]:
if not nums:
return None
mid = len(nums) // 2
root = TreeNode(nums[mid])
root.left = self.sortedArrayToBST(nums[:mid])
root.right = self.sortedArrayToBST(nums[mid + 1:])
return root
def test_is_valid_bst3(self):
s = Solution()
node0 = TreeNode(0)
node1 = TreeNode(1)
node2 = TreeNode(2)
node3 = TreeNode(3)
node4 = TreeNode(4)
node5 = TreeNode(5)
node6 = TreeNode(6)
node3.left = node1
node3.right = node5
node5.left = node4
node5.right = node6
node1.left = node0
node1.right = node2
node2.right = TreeNode(3)
self.assertFalse(s.isValidBST(node3))
def test_is_balanced2(self):
s = Solution()
node1 = TreeNode(1)
node2 = TreeNode(2)
node3 = TreeNode(3)
node4 = TreeNode(4)
node2.left = node1
node2.right = node3
node1.left = node4
node4.left = TreeNode(5)
self.assertFalse(s.isBalanced(node2))
def buildTree(self, preorder: List[int], inorder: List[int]) -> Optional[TreeNode]:
if not inorder:
return None
v = preorder.pop(0)
i = inorder.index(v)
root = TreeNode(v)
root.left = self.buildTree(preorder, inorder[:i])
root.right = self.buildTree(preorder, inorder[i + 1:])
return root
def vals_to_tree(self, vals: List[Optional[int]]) -> Optional[TreeNode]:
if not vals:
return None
val = vals.pop(0)
if val is None:
return None
root = TreeNode(val)
root.left = self.vals_to_tree(vals)
root.right = self.vals_to_tree(vals)
return root
def test_lowest_common_ancestor(self):
node0 = TreeNode(0)
node1 = TreeNode(1)
node2 = TreeNode(2)
node3 = TreeNode(3)
node4 = TreeNode(4)
node5 = TreeNode(5)
node6 = TreeNode(6)
node7 = TreeNode(7)
node8 = TreeNode(8)
node3.left = node5
node3.right = node1
node5.left = node6
node5.right = node2
node1.left = node0
node1.right = node8
node2.left = node7
node2.right = node4
s = Solution()
print(s.lowestCommonAncestor(node3, node5, node1).val)
print(s.lowestCommonAncestor(node3, node5, node4).val)
def process(self, start: int, end: int) -> List[Optional[TreeNode]]:
if start > end:
return [None]
res: List[TreeNode] = []
for i in range(start, end + 1):
left_list = self.process(start, i - 1)
right_list = self.process(i + 1, end)
for left in left_list:
for right in right_list:
root = TreeNode(i)
root.left = left
root.right = right
res.append(root)
return res
def process(self, head) -> Optional[TreeNode]:
if not head:
return None
if not head.next:
return TreeNode(head.val)
# 先得到 链表的 left_mid 节点
left_mid = self.get_left_mid(head)
mid = left_mid.next
root = TreeNode(mid.val)
# 将链表分为两段 left half and right half
lh = head
rh = mid.next
left_mid.next = None
# 递归
root.left = self.process(lh)
root.right = self.process(rh)
return root