def addOneRow(self, root: TreeNode, v: int, d: int) -> TreeNode:
"""Me"""
if not root or not d:
return root
level = 1
if d > 1:
level_nodes = []
queue = [root]
while queue:
length = len(queue)
if level == d - 1:
level_nodes = queue
break
for i in range(length):
node = queue.pop(0)
if node.left:
queue.append(node.left)
if node.right:
queue.append(node.right)
level += 1
for node in level_nodes:
tmp_left = node.left
node.left = TreeNode(v)
node.left.left = tmp_left
tmp_right = node.right
node.right = TreeNode(v)
node.right.right = tmp_right
else:
node = TreeNode(v)
node.left = root
return node
# print(level_nodes)
return root
def minCameraCover(self, root: TreeNode) -> int:
"""
后序遍历
贪心算法
Return 0 if it's a leaf.
Return 1 if it's a parent of a leaf, with a camera on this node.
Return 2 if it's coverd, without a camera on this node.
"""
UNCOVERED, CAMERA, COVERED = range(3)
self.ans = 0
dummy = TreeNode(-1)
dummy.left = root
def dfs(node):
if not node:
return COVERED
left = dfs(node.left)
right = dfs(node.right)
if left == UNCOVERED or right == UNCOVERED:
self.ans += 1
return CAMERA
elif left == CAMERA or right == CAMERA:
return COVERED
else:
return UNCOVERED
dfs(dummy)
return self.ans
def build():
nonlocal i
if i == len(s):
return
val = ''
# 提取数字
while i < len(s) and (s[i].isdigit() or s[i] == '-'):
val += s[i]
i += 1
# 建立根节点
root = TreeNode(val)
# 如果有左子树
if i < len(s) and s[i] == '(':
# 跳过左括号
i += 1
root.left = build()
# 跳过右括号
i += 1
# 如果有右子树
if i < len(s) and s[i] == '(':
# 跳过左括号
i += 1
root.right = build()
# 跳过右括号
i += 1
return root
def test_solution2():
root = TreeNode(-1,
left=TreeNode(-1, TreeNode(-1), TreeNode(-1)),
right=TreeNode(-1))
findElements = FindElements(root)
assert findElements.find(1)
assert findElements.find(3)
assert not findElements.find(5)
def rebuild(l):
if l[0] == "None":
l.pop(0)
return None
root = TreeNode(l.pop(0))
root.left = rebuild(l)
root.right = rebuild(l)
return root
def helper(l, r):
if l == r:
return None
mid = (l + r) // 2
root = TreeNode(nums[mid])
root.left = helper(l, mid)
root.right = helper(mid + 1, r)
return root
def test_solution3():
root = TreeNode(-1,
right=TreeNode(-1, left=TreeNode(-1, left=TreeNode(-1))))
findElements = FindElements(root)
assert findElements.find(2)
assert not findElements.find(3)
assert not findElements.find(4)
assert findElements.find(5)
def invertTree(self, root: TreeNode) -> TreeNode:
if not root:
return root
left = self.invertTree(root.right)
right = self.invertTree(root.left)
root.left = left
root.right = right
return root
def insertIntoBST(self, root: TreeNode, val: int) -> TreeNode:
node = TreeNode(val)
if not root: return node
if val > root.val:
root.right = self.insertIntoBST(root.right, val)
else:
root.left = self.insertIntoBST(root.left, val)
return root
def helper(start, end):
if start > end:
return None
mid = (start + end) >> 1
root = TreeNode(nums[mid])
root.left = helper(start, mid - 1)
root.right = helper(mid + 1, end)
return root
def buildTree(self, preorder, inorder):
if not inorder:
return None # inorder is empty
root = TreeNode(preorder[0])
root_pos = inorder.index(preorder[0])
root.left = self.buildTree(preorder[1: 1 + root_pos], inorder[: root_pos])
root.right = self.buildTree(preorder[root_pos + 1:], inorder[root_pos + 1:])
return root
def sortedArrayToBstHelper(arr, i, j):
if i >= j:
return None
mid = (i + j) // 2
node = TreeNode(arr[mid])
node.left = sortedArrayToBstHelper(arr, i, mid)
node.right = sortedArrayToBstHelper(arr, mid + 1, j)
return node
def builder():
val = next(chunk_iter)
if val == '#':
return None
node = TreeNode(int(val))
node.left = builder()
node.right = builder()
return node
def buildPreOrder():
val = data_list.pop(0)
if val == "#":
return None
node = TreeNode(int(val))
node.left = buildPreOrder()
node.right = buildPreOrder()
return node
def helper(l):
if l[0] == "#":
l.pop(0)
return None
root = TreeNode(l.pop(0))
root.left = helper(l)
root.right = helper(l)
return root
def removeLeafNodes(self, root: TreeNode, target: int) -> TreeNode:
if not root:
return None
root.left = self.removeLeafNodes(root.left, target)
root.right = self.removeLeafNodes(root.right, target)
if root.left is None and root.right is None and root.val == target:
return None
return root
def mergeTrees(self, t1: TreeNode, t2: TreeNode) -> TreeNode:
if not t1:
return t2
if not t2:
return t1
t = TreeNode(t1.val + t2.val)
t.left = self.mergeTrees(t1.left, t2.left)
t.right = self.mergeTrees(t1.right, t2.right)
return t
def sufficientSubset(self, root: TreeNode, limit: int) -> TreeNode:
if root.left == root.right:
return None if root.val < limit else root
if root.left:
root.left = self.sufficientSubset(root.left, limit - root.val)
if root.right:
root.right = self.sufficientSubset(root.right, limit - root.val)
return root if root.left or root.right else None
def flatten(self, root: TreeNode) -> None:
if root is None:
return None
if root:
self.flatten(root.right)
self.flatten(root.left)
root.right = self.prev
root.left = None
self.prev = root
def buildRecu(in_start, in_end):
if in_start == in_end:
return None
val = preorder.pop(0)
root = TreeNode(val)
idx = lookup[val]
root.left = buildRecu(in_start, idx)
root.right = buildRecu(idx + 1, in_end)
return root
def helper(start, end):
# print(start, end)
if start > end:
return None
max_val = max(nums[start:end + 1])
max_index = lookup[max_val]
root = TreeNode(max_val)
root.left = helper(start, max_index - 1)
root.right = helper(max_index + 1, end)
return root
def helper(in_start, in_end):
if in_start == in_end:
return None
node_val = postorder.pop()
node = TreeNode(node_val)
index = inorder_lookup[node_val]
# print("Node", node_val, in_start, in_end)
node.right = helper(index + 1, in_end)
node.left = helper(in_start, index)
return node
def buildTreeRecurse(pre_start, in_start, in_end):
if in_start == in_end:
return None
node_val = preorder[pre_start]
node = TreeNode(node_val)
idx = inorder_lookup[node_val]
# print("pre_start,idx,in_start", pre_start,idx ,in_start)
node.left = buildTreeRecurse(pre_start + 1, in_start, idx)
# 得到左子树中的节点数目 idx - in_start
node.right = buildTreeRecurse(pre_start + 1 + idx - in_start, idx + 1, in_end)
return node
def helper(in_start, in_end):
# nonlocal pre_idx
if in_start == in_end:
return None
node_val = preorder.pop(0)
node = TreeNode(node_val)
index = inorder_lookup[node_val]
# pre_idx += 1
node.left = helper(in_start, index)
node.right = helper(index + 1, in_end)
return node
def buildTreeRecursive(post_end, in_start, in_end):
if in_start == in_end:
return None
node_val = postorder[post_end - 1]
node = TreeNode(node_val)
idx = inorder_lookup[node_val]
# print("post_end,idx,in_start", post_end, idx, in_end)
node.left = buildTreeRecursive(post_end - 1 - (in_end - idx - 1),
in_start, idx)
node.right = buildTreeRecursive(post_end - 1, idx + 1, in_end)
return node
def helper(lower=-math.inf, upper=math.inf):
if self.idx == N:
return None
val = preorder[self.idx]
if val < lower or val > upper:
return None
self.idx += 1
root = TreeNode(val)
root.left = helper(lower, val)
root.right = helper(val, upper)
return root
def test_solutions1():
sol = Solution()
pA = TreeNode(4)
qA = TreeNode(5, TreeNode(6), TreeNode(2, TreeNode(7), pA))
rootA = TreeNode(3, left=qA, right=TreeNode(1, TreeNode(0), TreeNode(8)))
resA = sol.lowestCommonAncestor(rootA, pA, qA)
assert repr(resA) == repr(qA)
def test_solution(SolutionCLS):
root = TreeNode(7, TreeNode(3), TreeNode(15, TreeNode(9), TreeNode(20)))
iterator = SolutionCLS(root)
assert iterator.next() == 3
assert iterator.next() == 7
assert iterator.hasNext() == True
assert iterator.next() == 9
assert iterator.hasNext() == True
assert iterator.next() == 15
assert iterator.hasNext() == True
assert iterator.next() == 20
assert iterator.hasNext() == False
def trimBST(self, root: TreeNode, L: int, R: int) -> TreeNode:
if not root:
return root
elif root.val < L:
return self.trimBST(root.right, L, R)
elif root.val > R:
return self.trimBST(root.left, L, R)
else:
root.left = self.trimBST(root.left, L, R)
root.right = self.trimBST(root.right, L, R)
return root
def insertIntoMaxTree(self, root: TreeNode, val: int) -> TreeNode:
"""TODO"""
node = TreeNode(val)
if not root:
return node
if val > root.val:
node.left = root
return node
cur = root
while cur.right and cur.right.val > val:
cur = cur.right
cur.right, node.left = node, cur.right
return root