问题描述
我有一个find_successor函数，我想调用current.parent，但我意识到它是None类型，因为在我的insert（）中，我从未将parent用作指针。我想知道如何在不必过多修改代码的情况下将父指针实现到我的insert（）中。
class Node(object):
def __init__(self,data):
self.parent = None
self.left = None
self.right = None
self.data = data
class Tree(object):
PREORDER = 1
InorDER = 2
postorder = 3
def __init__(self):
# Do not create any other private variables.
# You may create more helper methods as needed.
self.root = None
def print(self):
# Print the data of all nodes in order
self.__print(self.root)
def __print(self,curr_node):
# Recursively print a subtree (in order),rooted at curr_node
if curr_node is not None:
self.__print(curr_node.left)
print(str(curr_node.data),end=' ') # save space
self.__print(curr_node.right)
def insert(self,data):
# Find the right spot in the tree for the new node
# Make sure to check if anything is in the tree
# Hint: if a node n is null,calling n.getData() will cause an error
if self.root is None:
self.root = Node(data)
else:
current = self.root
while True:
if current.data > data:
if current.left == None:
current.left = Node(data)
else:
current = current.left
elif current.data < data:
if current.right == None:
current.right = Node(data)
break
else:
current = current.right
else:
break
这是我正在使用的find_successor函数，可以在其中使用辅助方法来找到节点，但它没有父节点。
def find_successor(self,data):
# helper method to implement the delete method but may be called on its own
# if the right subtree of the node is nonempty,then the successor is just
# the leftmost node in the right subtree.
# If the right subtree of the node is empty,then go up the tree until a node that is
# the left child of its parent is encountered. The parent of the found node will be the
# successor to the initial node.
# Return object of successor if found else return None
current = self.__find_node(data)
if current.right:
while (current.right):
current = current.right
if current.left:
current = current.left
else:
return current
return current
else:
print(current.parent.data)
def __find_node(self,data):
# returns the node with that particular data value else returns None
current = self.root
while current is not None:
if (data > current.data):
current = current.right
elif (data < current.data):
current = current.left
elif (data == current.data):
return current
return None
这是我的测试用例
class T3_successor(unittest.TestCase)`:
def test_successor(self):
print("\n")
print("successor function")
tree_success = lab3.Tree()
tree_success.insert(8)
tree_success.insert(3)
tree_success.insert(10)
tree_success.insert(1)
tree_success.insert(6)
tree_success.insert(4)
tree_success.insert(7)
tree_success.insert(14)
tree_success.insert(13)
easy_success =tree_success.find_successor(8).data
medium_success = tree_success.find_successor(10).data
tough_success = tree_success.find_successor(7).data
self.assertEqual(easy_success,10)
self.assertEqual(medium_success,13)
self.assertEqual(tough_success,8)
print("\n")
解决方法
应该不会太复杂：在您的insert()方法中，当您将节点设置为新节点时，还将它们的父级（现在就不用了）设置为您来自的最后一个节点。
当您执行此操作时，根节点以外的每个节点都将根据需要具有指向其父节点的指针。