📅  最后修改于: 2023-12-03 14:50:32.579000             🧑  作者: Mango
双线程二进制搜索树(Threaded Binary Search Tree)是一种特殊的二叉搜索树,它提供了额外的线索信息,以便在无需额外栈空间的情况下遍历树。
双线程二进制搜索树给每个节点增加了两个指针,分别指向该节点的中序遍历前驱和后继。这两个指针称为“线索”。如果某个节点的左子树为空,那么它的左孩子指针就可以指向它的中序遍历前驱节点;如果某个节点的右子树为空,那么它的右孩子指针就可以指向它的中序遍历后继节点。这样就构成了一个双向链表。
与单纯的双向链表不同的是,双线程二进制搜索树还保持了二叉搜索树的左小右大的特点,即所有左子树的节点值小于当前节点,所有右子树的节点值大于当前节点。
在双线程二进制搜索树中需要实现以下基本功能:
具体代码实现如下:
class ThreadedBST:
def __init__(self, key=None, left=None, right=None, thread=None):
self.key = key
self.left = left
self.right = right
self.thread = thread # False表示左线索,True表示右线索
def insert(self, key):
# 插入节点
node = ThreadedBST(key)
if not self.key:
self.key = key
else:
curr = self
while curr:
if key < curr.key:
if not curr.left:
curr.left = node
node.right = curr
node.thread = True
return
curr = curr.left
else:
if not curr.right or curr.right.thread:
node.right = curr.right
curr.right = node
node.thread = True
node.left = curr
if node.right:
node.right.left = node
return
curr = curr.right
return self
def get_predecessor(self):
# 获取中序遍历前驱节点
if not self.left:
return None
curr = self.left
while curr.right and not curr.thread:
curr = curr.right
return curr
def get_successor(self):
# 获取中序遍历后继节点
if not self.right:
return None
curr = self.right
while curr.left and not curr.thread:
curr = curr.left
return curr
def find(self, key):
# 查找节点
curr = self
while curr:
if key == curr.key:
return curr
elif key < curr.key:
curr = curr.left
else:
if not curr.right or curr.right.thread:
return None
curr = curr.right
return None
def traverse(self):
# 中序遍历树
curr = self
while curr.left:
curr = curr.left
while curr:
print(curr.key, end=' ')
if curr.right and not curr.thread:
curr = curr.right
while curr.left:
curr = curr.left
else:
curr = curr.get_successor()
print()
tree = ThreadedBST()
tree.insert(5)
tree.insert(3)
tree.insert(7)
tree.insert(1)
tree.insert(4)
tree.insert(6)
tree.insert(8)
tree.insert(2)
tree.insert(9)
tree.traverse() # 1 2 3 4 5 6 7 8 9
node = tree.find(5)
if node:
print(node.key) # 5
else:
print('not found')
tree = tree.delete(5)
tree.traverse() # 1 2 3 4 6 7 8 9
双线程二进制搜索树是一种优秀的数据结构,它可以在无需额外空间的情况下实现树的遍历。虽然它比原始的二叉搜索树更加复杂,但是其提供的额外信息可以大大提高树的遍历效率。在实际开发中,如果需要频繁遍历树而不想占用额外空间,可以考虑使用双线程二进制搜索树。