我正在尝试以“图形”方式打印二进制搜索树（prettyPrint函数会这样做）。
我的node类看起来像这样：
class Node:
def __init__(self, dataValue):
self.dataValue = dataValue
self.leftChild = None
self.rightChild = None
我的tree类看起来像这样：
class binary_search_tree(Node):
def __init__(self):
self.root = None
def insert(self, value):
if self.root is None:
self.root = Node(value)
else:
self._insert(value, self.root)
def _insert(self, value, cur_node):
if value < cur_node.dataValue:
if cur_node.leftChild is None:
cur_node.leftChild = Node(value)
else:
self._insert(value, cur_node.leftChild)
if value > cur_node.dataValue:
if cur_node.rightChild is None:
cur_node.rightChild = Node(value)
else:
self._insert(value, cur_node.rightChild)
def print_tree(self, transversal_type):
if transversal_type == "preorder":
return self._print_preorder(self.root, "")
elif transversal_type == "inorder":
return self._print_inorder(self.root, "")
elif transversal_type == "postorder":
return self._print_postorder(self.root, "")
else:
print("{} does not exist".format(transversal_type))
return False
def _print_tree(self, root, indent, transversal = ""):
if root is not None:
self._print_tree(root.rightChild, indent + " ")
transversal += indent + str(root.dataValue)
self._print_tree(root.leftChild, indent + " ")
return transversal
def _print_preorder(self, start, transversal):
# Root -> Left -> Right
if start:
transversal += (str(start.dataValue) + " - ")
transversal = self._print_preorder(start.leftChild, transversal)
transversal = self._print_preorder(start.rightChild, transversal)
return transversal
def _print_inorder(self, start, transversal):
#Left -> Root -> Right
if start:
transversal = self._print_inorder(start.leftChild, transversal)
transversal += (str(start.dataValue) + " - ")
transversal = self._print_inorder(start.rightChild, transversal)
return transversal
def _print_postorder(self, start, transversal):
#Left -> Right -> Root
if start:
transversal = self._print_postorder(start.leftChild, transversal)
transversal = self._print_postorder(start.rightChild, transversal)
transversal += (str(start.dataValue) + " - ")
return transversal
def search(self, value):
if self.root!=None:
return self._search(value,self.root)
else:
return False
def _search(self, value, cur_node):
if value==cur_node.dataValue:
return True
elif value < cur_node.dataValue and cur_node.leftChild!=None:
return self._search(value, cur_node.leftChild)
elif value > cur_node.dataValue and cur_node.rightChild!=None:
return self._search(value, cur_node.rightChild)
return False
def min_value(self, node):
current = node
while(current.leftChild is not None):
current = current.leftChild
return current
def delete_node(self, node, value):
if node is None:
return node
if value < node.dataValue:
node.leftChild = self.delete_node(node.leftChild, value)
elif value > node.dataValue:
node.rightChild = self.delete_node(node.rightChild, value)
else:
if node.leftChild is None:
temp = node.rightChild
node = None
return temp
elif node.rightChild is None:
temp = node.leftChild
node = None
return temp
temp = self.min_value(node)
node.dataValue = temp.dataValue
node.rightChild = self
def getNumNodes(self):
if self.root:
return self._getNumNodes(self.root)
else:
return 0
def _getNumNodes(self, node):
total = 1
if node.leftChild:
total += self._getNumNodes(node.leftChild)
if node.rightChild:
total += self._getNumNodes(node.rightChild)
return total
def getHeight(self):
return self._getHeight(self.root)
def _getHeight(self, node):
if not node:
return 0
else:
return max(self._getHeight(node.leftChild), self._getHeight(node.rightChild)) + 1
def fillTree(self, height):
self._fillTree(self.root, height)
def _fillTree(self, node, height):
if height <= 1:
return
if node:
if not node.leftChild: node.leftChild = Node(' ')
if not node.rightChild: node.rightChild = Node(' ')
self._fillTree(node.leftChild, height - 1)
self._fillTree(node.rightChild, height - 1)
def prettyPrint(self):
"""
"""
# get height of tree
total_layers = self.getHeight()
tree = deepcopy(self)
tree.fillTree(total_layers)
# start a queue for BFS
queue = Queue()
# add root to queue
queue.enqueue(tree) # self = root
# index for 'generation' or 'layer' of tree
gen = 1
# BFS main
while not queue.isEmpty():
# copy queue
#
copy = Queue()
while not queue.isEmpty():
copy.enqueue(queue.dequeue())
#
# end copy queue
first_item_in_layer = True
edges_string = ""
extra_spaces_next_node = False
# modified BFS, layer by layer (gen by gen)
while not copy.isEmpty():
root = copy.dequeue()
# -----------------------------
# init spacing
spaces_front = pow(2, total_layers - gen + 1) - 2
spaces_mid = pow(2, total_layers - gen + 2) - 2
dash_count = pow(2, total_layers - gen) - 2
if dash_count < 0:
dash_count = 0
spaces_mid = spaces_mid - (dash_count * 2)
spaces_front = spaces_front - dash_count
init_padding = 2
spaces_front += init_padding
if first_item_in_layer:
edges_string += " " * init_padding
# ----------------------------->
# -----------------------------
# construct edges layer
edge_sym = "/" if root.leftChild and root.leftChild.data is not " " else " "
if first_item_in_layer:
edges_string += " " * (pow(2, total_layers - gen) - 1) + edge_sym
else:
edges_string += " " * (pow(2, total_layers - gen + 1) + 1) + edge_sym
edge_sym = "\\" if self.root.rightChild and self.root.rightChild.data is not " " else " "
edges_string += " " * (pow(2, total_layers - gen + 1) - 3) + edge_sym
# ----------------------------->
# -----------------------------
# conditions for dashes
if self.root.leftChild and self.root.leftChild.data == " ":
dash_left = " "
else:
dash_left = "_"
if self.root.rightChild and self.root.rightChild.data == " ":
dash_right = " "
else:
dash_right = "_"
# ----------------------------->
# -----------------------------
# handle condition for extra spaces when node lengths don't match or are even:
if extra_spaces_next_node:
extra_spaces = 1
extra_spaces_next_node = False
else:
extra_spaces = 0
# ----------------------------->
# -----------------------------
# account for longer data
data_length = len(str(self.root.data))
if data_length > 1:
if data_length % 2 == 1: # odd
if dash_count > 0:
dash_count -= ((data_length - 1) / 2)
else:
spaces_mid -= (data_length - 1) / 2
spaces_front -= (data_length - 1) / 2
if data_length is not 1:
extra_spaces_next_node = True
else: # even
if dash_count > 0:
dash_count -= ((data_length) / 2) - 1
extra_spaces_next_node = True
# dash_count += 1
else:
spaces_mid -= (data_length - 1)
spaces_front -= (data_length - 1)
# ----------------------------->
# -----------------------------
# print node with/without dashes
if first_item_in_layer:
print(str(" " * spaces_front) + str(dash_left * dash_count) + str(node.data) + str(dash_right * dash_count), end="")
first_item_in_layer = False
else:
print((" " * (spaces_mid - extra_spaces)) + (dash_left * dash_count) + (self.root.data) + (dash_right * dash_count), end=""),
# ----------------------------->
if self.root.leftChild: queue.enqueue(self.root.leftChild)
if self.root.rightChild: queue.enqueue(self.root.rightChild)
# print the fun squiggly lines
if not queue.isEmpty():
print("\n" + edges_string)
gen += 1
我得到的错误是'binary_search_tree' object has no attribute 'leftChild'，在代码的这一部分：
edge_sym = "/" if root.leftChild and root.leftChild.data is not " " else " "
我猜我已经使类“冲突”了，但是我不知道如何解决。
答案 0 :(得分：0)
您的代码是不完整的，实际上并不是最小的可复制示例。但看起来像
在这里复制binary_search_tree对象
tree = deepcopy(self)
然后假设树是您的根对象，又名Node
queue.enqueue(tree) # self = root
这是不正确的，因为您的根节点将是tree.root。
这至少解决了您目前的问题，但是还有更多问题，例如尝试从名为.data的节点打印.dataValue。