def buildChildTree(pre_l: int, pre_r: int, ino_l: int, ino_r: int) -> TreeNode or None:
root = None
if pre_l <= pre_r:
root = TreeNode(preorder[pre_l])
index = dic[preorder[pre_l]]
size_l = index - ino_l
root.left = buildChildTree(pre_l + 1, pre_l + size_l, ino_l, ino_l + size_l - 1)
root.right = buildChildTree(pre_l + 1 + size_l, pre_r, ino_l + size_l + 1, ino_r)
return root
def recurseMerge(node1: TreeNode, node2: TreeNode) -> None or TreeNode:
if not node1:
return node2
if not node2:
return node1
result = TreeNode(node1.val + node2.val)
result.left = recurseMerge(node1.left, node2.left)
result.right = recurseMerge(node1.right, node2.right)
return result
def constructChild(the_num: List[int]) -> TreeNode or None:
if the_num:
index = 0
for indexes in range(0, len(the_num)):
if the_num[indexes] > the_num[index]:
index = indexes
result = TreeNode(the_num[index])
result.left = constructChild(the_num[:index])
result.right = constructChild(the_num[index + 1:])
return result
def constructChild(left_index: int, right_index: int) -> TreeNode or None:
if left_index != right_index:
index = cur = left_index
while cur < right_index:
if nums[cur] > nums[index]:
index = cur
cur += 1
result = TreeNode(nums[index])
result.left = constructChild(left_index, index)
result.right = constructChild(index + 1, right_index)
return result
def recursion(pre: List[int], ino: List[int]) -> TreeNode or None:
root = None
if pre:
root = TreeNode(pre[0])
index = 0
# 每次都线性查找
while index <= len(ino) - 1:
if ino[index] != pre[0]:
index += 1
else:
break
root.left = recursion(pre[1:1 + index], ino[:index])
root.right = recursion(pre[1 + index:], ino[index + 1:])
return root
def constructMaximumBinaryTree(nums: List[int]) -> TreeNode or None:
if nums:
nodes = []
for num in nums:
cur = TreeNode(num)
if not nodes or cur.val <= nodes[-1].val:
nodes.append(cur)
continue
while cur.val > nodes[-1].val:
child = nodes.pop()
if not nodes or nodes[-1].val > cur.val:
cur.left = child
else:
nodes[-1].right = child
if not nodes:
break
nodes.append(cur)
while len(nodes) > 1:
child = nodes.pop()
nodes[-1].right = child
return nodes[0]
def recurseMerge(nodes: List[TreeNode]) -> None or TreeNode:
if not nodes[0] and not nodes[1]:
return
result = TreeNode()
left = []
right = []
if nodes[0]:
result.val += nodes[0].val
left.append(nodes[0].left)
right.append(nodes[0].right)
else:
left.append(None)
right.append(None)
if nodes[1]:
result.val += nodes[1].val
left.append(nodes[1].left)
right.append(nodes[1].right)
else:
left.append(None)
right.append(None)
result.left = recurseMerge(left)
result.right = recurseMerge(right)
return result
