代码如下:
class BinaryTree:
def __init__(self,rootObj):
self.key = rootObj
self.left = None
self.right = None
root = [self.key, self.left, self.right]
def getRootVal(root):
return root[0]
def setRootVal(newVal):
root[0] = newVal
def getLeftChild(root):
return root[1]
def getRightChild(root):
return root[2]
def insertLeft(self,newNode):
if self.left == None:
self.left = BinaryTree(newNode)
else:
t = BinaryTree(newNode)
t.left = self.left
self.left = t
def insertRight(self,newNode):
if self.right == None:
self.right = BinaryTree(newNode)
else:
t = BinaryTree(newNode)
t.right = self.right
self.right = t
def buildParseTree(fpexp):
fplist = fpexp.split()
pStack = Stack()
eTree = BinaryTree('')
pStack.push(eTree)
currentTree = eTree
for i in fplist:
if i == '(':
currentTree.insertLeft('')
pStack.push(currentTree)
currentTree = currentTree.getLeftChild()
elif i not in '+-*/)':
currentTree.setRootVal(eval(i))
parent = pStack.pop()
currentTree = parent
elif i in '+-*/':
currentTree.setRootVal(i)
currentTree.insertRight('')
pStack.push(currentTree)
currentTree = currentTree.getRightChild()
elif i == ')':
currentTree = pStack.pop()
else:
print "error: I don't recognize " + i
return eTree
def postorder(tree):
if tree != None:
postorder(tree.getLeftChild())
postorder(tree.getRightChild())
print tree.getRootVal()
def preorder(self):
print self.key
if self.left:
self.left.preorder()
if self.right:
self.right.preorder()
def inorder(tree):
if tree != None:
inorder(tree.getLeftChild())
print tree.getRootVal()
inorder(tree.getRightChild())
class Stack:
def __init__(self):
self.items = []
def isEmpty(self):
return self.items == []
def push(self, item):
self.items.append(item)
def pop(self):
return self.items.pop()
def peek(self):
return self.items[len(self.items)-1]
def size(self):
return len(self.items)
def main():
parseData = raw_input( "Please enter the problem you wished parsed.(NOTE: problem must have parenthesis to seperate each binary grouping and must be spaced out.) " )
tree = buildParseTree(parseData)
print( "The post order is: ", + postorder(tree))
print( "The post order is: ", + postorder(tree))
print( "The post order is: ", + preorder(tree))
print( "The post order is: ", + inorder(tree))
main()
下面是错误:
Please enter the problem you wished parsed.(NOTE: problem must have parenthesis to seperate each binary grouping and must be spaced out.) ( 1 + 2 ) Traceback (most recent call last): File "C:\Users\Kevin\Desktop\Python Stuff\Assignment 11\parseTree.py", line 108, in main() File "C:\Users\Kevin\Desktop\Python Stuff\Assignment 11\parseTree.py", line 102, in main tree = buildParseTree(parseData) File "C:\Users\Kevin\Desktop\Python Stuff\Assignment 11\parseTree.py", line 46, in buildParseTree currentTree = currentTree.getLeftChild() File "C:\Users\Kevin\Desktop\Python Stuff\Assignment 11\parseTree.py", line 15, in getLeftChild return root[1] AttributeError: BinaryTree instance has no attribute '__getitem__'
因为你声明你的方法是错误的:
让我们看看如果调用
tree.getRootVal()
会发生什么。.getRootVal()
是这样声明的:您可能知道,传递给方法的第一个参数始终是实例,并且是隐式提供的。所以你基本上试着把
BinaryTree
的一个实例看作一个序列(root[0]
)。必须这样指定:
对象方法的第一个参数不必调用
self
。但是这样做有助于避免像你这样的错误。有趣的是,您正确地声明了
insertLeft
和insertRight
;)第一个问题是
root
应该是self.root
。第二个问题是:
你在用新的意义重新定义根。
正如前奏曲和赋格曲所说,你应该修正格式。但据我所知,在BinaryTree中的类方法中至少有一个错误:它们中的大多数甚至不把
self
作为参数。解决这个问题,也许你会好一点。相关问题 更多 >
编程相关推荐