def construct_core(preorder, start_preorder, end_preorder, inorder,
start_inorder, end_inorder):
"""
先根据前序遍历序列的第一个数字创建根结点，接下来在中序遍历序列中找到根结点的位置，
这样就能确定左、右子树结点的数量。在前序遍历和中序遍历的序列中划分了左、右子树结
点的值之后，就可以递归地去分别构建它的左右子树。
:param preorder:
:param start_preorder:
:param end_preorder:
:param inorder:
:param start_inorder:
:param end_inorder:
:return:
"""
# 前序遍历的第一个数字是根结点的值
root_value = preorder[start_preorder]
root = BinTree(root=root_value)
root.left = root.right = None
root.data = root.root
if start_preorder == end_preorder:
if start_inorder == end_inorder and inorder[start_inorder] == inorder[
end_inorder]:
return root
else:
raise Exception("错误的输入")
# 在中序遍历中找到根结点的值
root_inorder = start_inorder
while root_inorder <= end_inorder and inorder[root_inorder] != root_value:
root_inorder += 1
# 如果两个序列不匹配
if root_inorder == end_inorder and inorder[root_inorder] != root_value:
raise Exception("两个序列不匹配!", root_value, inorder[root_value])
left_length = root_inorder - start_inorder
left_preorder_end = start_preorder + left_length
# 构建左子树
if left_length > 0:
root.left = construct_core(preorder, start_preorder + 1,
left_preorder_end, inorder, start_inorder,
root_inorder - 1)
# 构建右子树
if left_length < end_preorder - start_preorder:
# root.right = construct_core(preorder, left_preorder_end + 1, end_preorder, inorder, root_inorder + 1,
# end_inorder)
root.right = construct_core(preorder, left_preorder_end + 1,
end_preorder, inorder, root_inorder + 1,
end_inorder)
return root
