我一直在尝试实现splay树但到目前为止没有成功。以前我成功实现了二叉搜索树和avl树，因为splay树是二叉搜索树的变种，所以插入代码和旋转代码很好。我面临的唯一问题是每次插入节点时将节点移动到根。这是我的代码
class SplayTree:
def __init__(self):
self.root = None
self.size = 0
def moveUp(self, currentNode):
if currentNode.parent:
if currentNode.parent.parent is not None:
#zig zag
if currentNode.isRightChild() and currentNode.parent.isLeftChild():
self.rotateLeft(currentNode.parent)
self.rotateRight(currentNode.parent)
elif currentNode.isLeftChild() and currentNode.parent.isRightChild():
self.rotateRight(currentNode.parent)
self.rotateLeft(currentNode.parent)
#zig zig
if currentNode.isLeftChild() and currentNode.parent.isLeftChild():
self.rotateRight(currentNode.parent.parent)
self.rotateRight(currentNode.parent)
elif currentNode.isRightChild() and currentNode.parent.isRightChild():
self.rotateLeft(currentNode.parent.parent)
self.rotateLeft(currentNode.parent)
self.moveUp(currentNode)
#zig
if currentNode.isLeftChild():
self.rotateRight(currentNode.parent)
elif currentNode.isRightChild():
self.rotateLeft(currentNode.parent)
self.moveUp(currentNode)
else:
return
def put(self,key,val):
if self.root:
self._put(key,val,self.root)
else:
self.root = TreeNode(key,val)
self.size += 1
def _put(self,key,val,currentNode):
if key < currentNode.key:
if currentNode.hasLeftChild():
self._put(key,val,currentNode.leftChild)
else:
currentNode.leftChild = TreeNode(key,val,parent=currentNode)
self.moveUp(currentNode.leftChild)
else:
if currentNode.hasRightChild():
self._put(key,val,currentNode.rightChild)
else:
currentNode.rightChild = TreeNode(key,val,parent=currentNode)
self.moveUp(currentNode.rightChild)
def __setitem__(self, key, value):
self.put(key,value)
def rotateLeft(self, rotRoot):
newRoot = rotRoot.rightChild
if newRoot.leftChild is not None:
rotRoot.rightChild = newRoot.leftChild
newRoot.leftChild.parent = rotRoot
# if subtree is at top or somewhere in between
# make connection between node and parent
newRoot.parent = rotRoot.parent
if rotRoot.parent is None:
self.root = newRoot
# make connection between parent and node
else:
if rotRoot.isLeftChild():
rotRoot.parent.leftChild = newRoot
else:
rotRoot.parent.rightChild = newRoot
newRoot.leftChild = rotRoot
rotRoot.parent = newRoot
def rotateRight(self, rotRoot):
newRoot = rotRoot.leftChild
if newRoot.rightChild is not None:
rotRoot.leftChild = newRoot.rightChild
newRoot.rightChild.parent = rotRoot
newRoot.parent = rotRoot.parent
if rotRoot.parent is None:
self.root = newRoot
else:
if rotRoot.isLeftChild():
rotRoot.parent.leftChild = newRoot
else:
rotRoot.parent.rightChild = newRoot
newRoot.rightChild = rotRoot
rotRoot.parent = newRoot
def inorder(self):
print("INORDER")
if self.root:
self._inorder(self.root)
print()
else:
return None
def _inorder(self,currentNode):
if currentNode:
self._inorder(currentNode.leftChild)
print(currentNode.key,end=" ")
self._inorder(currentNode.rightChild)
class TreeNode:
def __init__(self,key,val,left = None,right = None,parent = None):
self.key = key
self.payload = val
self.leftChild = left
self.rightChild = right
self.parent = parent
def hasLeftChild(self):
return self.leftChild
def hasRightChild(self):
return self.rightChild
def isLeftChild(self):
return self.parent and self.parent.leftChild == self
def isRightChild(self):
return self.parent and self.parent.rightChild == self
def isLeaf(self):
return not (self.leftChild or self.rightChild)
def hasAnyChildren(self):
return self.leftChild or self.rightChild
def hasBothChildren(self):
return self.leftChild and self.rightChild
st = SplayTree()
st[32] = "Cat"
st[55] = "Dog"
st[10] = "Lion"
st[41] = "Zebra"
st[19] = "Fox"
st[1] = "Wolf"
st[16] = "Tiger"
st[12] = "Pig"
st.inorder()
我认为我的moveUp（）方法是出错的地方。但我似乎无法弄清楚到底出了什么问题？
答案 0 :(得分：1)
您的代码中存在两个问题。
第一个是你的轮换方法中有一个微妙的错误，有时候你应该没有设置一个到None的子链接。 rotRoot.rightChild = newRoot.leftChild中if中的第rotateLeft行（以及rotateRight中的等效行）应无条件运行。只需将其从if移出即可修复它。
第二个问题是您经常调用moveUp。您正在从每次递归调用_put运行它，但由于它moveUp也会递归调用自身，这意味着它运行得太频繁。缩进_put中的调用，使它们成为您创建新节点的else块的一部分。这样，您只会在上次moveUp来电时拨打_put，而不是全部来电。{/ p>
def _put(self,key,val,currentNode):
if key < currentNode.key:
if currentNode.hasLeftChild():
self._put(key,val,currentNode.leftChild)
else:
currentNode.leftChild = TreeNode(key,val,parent=currentNode)
self.moveUp(currentNode.leftChild) # increase indent here!
else:
if currentNode.hasRightChild():
self._put(key,val,currentNode.rightChild)
else:
currentNode.rightChild = TreeNode(key,val,parent=currentNode)
self.moveUp(currentNode.rightChild) # here too
def rotateLeft(self, rotRoot):
newRoot = rotRoot.rightChild
rotRoot.rightChild = newRoot.leftChild # move this line up, out of the if
if newRoot.leftChild is not None:
newRoot.leftChild.parent = rotRoot
newRoot.parent = rotRoot.parent
if rotRoot.parent is None:
self.root = newRoot
# make connection between parent and node
else:
if rotRoot.isLeftChild():
rotRoot.parent.leftChild = newRoot
else:
rotRoot.parent.rightChild = newRoot
newRoot.leftChild = rotRoot
rotRoot.parent = newRoot
def rotateRight(self, rotRoot):
newRoot = rotRoot.leftChild
rotRoot.leftChild = newRoot.rightChild # this one as well
if newRoot.rightChild is not None:
newRoot.rightChild.parent = rotRoot
newRoot.parent = rotRoot.parent
if rotRoot.parent is None:
self.root = newRoot
else:
if rotRoot.isLeftChild():
rotRoot.parent.leftChild = newRoot
else:
rotRoot.parent.rightChild = newRoot
newRoot.rightChild = rotRoot
rotRoot.parent = newRoot
答案 1 :(得分：0)
尝试在两个地方更改你的moveUp：
type *.txt 2>nul那应该有帮助