def helper(l, lo, hi):
if lo > hi:
return
mid = (lo + hi) >> 1
node = Node(l[mid])
node.left_child = helper(l, lo, mid - 1)
node.right_child = helper(l, mid + 1, hi)
return node
def convert_sorted_list_to_binary_search_tree(head):
if head is None:
return None
#龟兔算法找节点
fast = head
slow = head
pre = None
while fast is not None and fast.next is not None:
fast = fast.next.next
pre = slow
slow = slow.next
if pre is not None: # break link
pre.next = None
else:
head = None #递归返回：当链表只有一个节点时
root = Node(slow.data)
root.left_child = convert_sorted_list_to_binary_search_tree(head)
root.right_child = convert_sorted_list_to_binary_search_tree(slow.next)
return root
def test_node_left_child(self):
n1 = Node(4)
n2 = Node(2)
n1.left_child = n2
self.assertEqual(n2, n1.left_child)
self.assertEqual(2, n1.left_child.value)
