如果Google面试让你用python写一个树的遍历程序

前几天忽然对python很感兴趣，学了几天也感觉它非常的简洁实用。打破了我这么长时间对java C# C 和vb的审美疲劳，让我眼前一亮。“就像读英文一样简单”这句话评价python说的很合理。

我对python的好感很大部分是因为听说google很多程序用python，而且在google app engine里面和支持python。如果你去google面试或者笔试，很可能就会考到这个题：用python实现树的遍历。

自己试着写了一下，不过毕竟是菜鸟，有问题请多多指教。

运行效果如下：



源程序如下：

#!user/bin/python

#树的实体（包括 Id, value, fatherId）

class treeModel:

'''tree view'''

def __init__(self,Id,value,fatherId):

self.Id=Id

self.value=value

self.fatherId=fatherId

def show(self):

return self.value

# 树的遍历和展示

class treeShow:

'''tree show'''

logList = [treeModel(0,'addTree',0)] #记录已经遍历过的节点

writtenList = [treeModel(0,'addTree',0)] #记录已经打印出的节点

def __init__(self,rootId,list):

self.rootId = rootId

self.list=list

#通过Id获取节点

def getModelById(self,Id):

for t in self.list:

if t.Id == Id:

return t

return None

#判断是否有子节点

def haveChild(self,t):

for t1 in self.list:

if t1.fatherId == t.Id and not self.IsInLogList(t1):

return True

return False

#获取第一个没有遍历的子节点

def getFirstChild(self,t):

for t1 in self.list:

if t1.fatherId == t.Id and not self.IsInLogList(t1):

return t1

return None

#判断某节点是否已经被遍历

def IsInLogList(self,t):

for t1 in self.logList:

if t1.Id == t.Id:

return True

return False

#判断某节点是否已经打印

def IsInWrittenList(self,t):

for t1 in self.writtenList:

if t1.Id == t.Id:

return True

return False

#获取父节点

def getFatherTree(self,t):

for t1 in self.list:

if t1.Id == t.fatherId:

return t1

return None

#遍历打印

def show(self):

currentTree = self.getModelById(self.rootId)

s = ' '

strNum = 1

while(True):

if self.haveChild(currentTree):

if not self.IsInWrittenList(currentTree):

print s*strNum,currentTree.show()

self.writtenList.append(currentTree)

currentTree = self.getFirstChild(currentTree)

strNum += 1

continue

else:

if(currentTree.Id == self.rootId):

break

else:

if not self.IsInWrittenList(currentTree):

print s*strNum,currentTree.show()

self.logList.append(currentTree)

currentTree = self.getFatherTree(currentTree)

strNum -= 1

continue

#初始化一些节点实例

t1 = treeModel(1,'A-1',0)

t2 = treeModel(2,'B-1',1)

t3 = treeModel(3,'B-2',1)

t4 = treeModel(4,'C-1',2)

t5 = treeModel(5,'C-2',2)

t6 = treeModel(6,'C-3',3)

t7 = treeModel(7,'C-4',3)

t8 = treeModel(8,'D-1',4)

t9 = treeModel(9,'E-1',8)

t10 = treeModel(10,'E-2',8)

#将这些节点实例链式存储起来（就像数据库里存储一样）

list = [t1,t2,t3,t4,t5,t6,t7,t8,t9,t10]

#调用展示

ts = treeShow(1,list)

ts.show()