我有一个python脚本,该脚本生成了给定数学表达式的二进制树。我正在尝试编写一个函数以打印二进制树,如果我在级别订单中穿越它。
例如。如果函数为((2 3(-4(输出应为
-
/
+ 4
/
2 3
output:
-
+ 4
2 3
代码将数学表达式转换为二进制树
from pythonds.basic.stack import Stack
from pythonds.trees.binaryTree import BinaryTree
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(int(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:
raise ValueError
return eTree
我正在使用标准伪代码进行广度优先搜索。
printTree(Node root)
if(root == NULL) return
else
create a queue 'q'
q.enqueue(root)
while(q is not empty)
root = q.dequeue
print(root)
if(leftChild != NULL)
q.enqueue(leftChild)
if(rightChild != NULL)
q.enqueue(rightChild)
以下是我写的python代码,以打印树级。
import sys
class Node:
def __init__(self, data):
self.data = data
self.leftChild = None
self.rightChid = None
class Queue:
def __init__(self):
self.items = []
def isEmpty(self):
return self.items == []
def enqueue(self,item):
self.items.insert(0, item)
def dequeue(self):
self.items.pop()
def printNodesInLevels(root):
if root is None:
return
else:
q = Queue()
q.enqueue(root)
while(q is not None):
root = q.dequeue()
print(root.getRootVal())
if(root.leftChild is not None):
q.enqueue(root.leftChild)
if(root.rightChild is not None):
q.enqueue(root.rightChild)
这就是我调用函数的方式。
pt = buildParseTree("( ( 2 + 3 ) - 4 )")
printNodesInLevels(pt)
以下是我收到的错误消息。我认为我没有正确地将树的根传递到打印功能。
无
trackback(最近的最新通话(:文件 " c:/users/yasoda/pycharmprojects/helloworld/binarytree.py",第77行, 在 printNodesInlevels(pt(文件" c:/users/yasoda/pycharmprojects/helledorld/binarytree.py",第67行, 在printnodesinlevels中 if(root.leftchild不是一个(:attributeError:'nontype'对象没有属性'leftChild'
您的代码中有两个错误。第一个是,您需要返回Dequeue,
class Queue:
def __init__(self):
self.items = []
def isEmpty(self):
return self.items == []
def enqueue(self,item):
self.items.insert(0, item)
def dequeue(self):
return self.items.pop()
第二个在while循环中检查队列是否为空,
while(not q.isEmpty()):