11.二叉树
python实现二叉树的数据结构：

　　. 二叉树的排序方式：

　　　　- 广度遍历（层次遍历）

　　　　- 深度遍历：
　　　　　　- 前序（根左右）：把根放到最前面
　　　　　　- 中序（左根右）：把根放到中间
　　　　　　- 后序（左右根）：把根放到最后

class Node():
def init(self,item):
self.item = item
self.right = None
self.left = None
class Tree():
def init(self):
self.root = None
def add(self,item):
node = Node(item)
if self.root is None:
self.root = node
return
else:
queue = [self.root]
while queue:
cur = queue.pop(0)
if cur.left is None:
cur.left = node
return
else:
queue.append(cur.left)
if cur.right is None:
cur.right = node
return
else:
queue.append(cur.right)
#广度遍历
def travel(self):
if self.root is None:
print(‘‘)
return
else:
queue = [self.root]
while queue:
cur = queue.pop(0)
print(cur.item)
if cur.left is not None:
queue.append(cur.left)
if cur.right is not None:
queue.append(cur.right)

#深度遍历：前序，中序，后序遍历
def forwordTravel(self,root):
    if root is None:
        return
    print(root.item,end=‘ ‘)
    self.forwordTravel(root.left)
    self.forwordTravel(root.right)
    
def middleTravel(self,root):
    if root is None:
        return
    self.middleTravel(root.left)
    print(root.item,end=‘ ‘)
    self.middleTravel(root.right)
    
def backTravel(self,root):
    if root is None:
        return
    self.backTravel(root.left)
    self.backTravel(root.right)
    print(root.item,end=‘ ‘)

tree = Tree()
tree.add(‘0‘)
tree.add(‘1‘)
tree.add(‘2‘)
tree.add(‘3‘)
tree.add(‘4‘)
tree.add(‘5‘)
tree.add(‘6‘)
tree.add(‘7‘)
tree.add(‘8‘)
tree.add(‘9‘)

tree.travel()
tree.forwordTravel(tree.root)
print(‘\n‘)
tree.backTravel(tree.root)
print(‘\n‘)
tree.middleTravel(tree.root)
print(‘\n‘)

python实现排序二叉树：

排序二叉树

class Node():
def init(self,item):
self.item = item
self.left = None
self.right = None
class Tree():
def init(self):
self.root = None
def insert(self,item):
node = Node(item)
cur = self.root
if cur is None:
self.root = node
return
while True:
if item < cur.item:
if cur.left is None:
cur.left = node
return
else:
cur = cur.left
else:
if cur.right is None:
cur.right = node
return
else:
cur = cur.right
def preTravel(self,root):
if root is None:
return
print(root.item,end=‘ ‘)
self.preTravel(root.left)
self.preTravel(root.right)
def middleTravel(self,root):
if root is None:
return
self.middleTravel(root.left)
print(root.item,end=‘ ‘)
self.middleTravel(root.right)
def backTravel(self,root):
if root is None:
return
self.backTravel(root.left)
self.backTravel(root.right)
print(root.item,end=‘ ‘)

tree = Tree()
tree.insert(3)
tree.insert(8)
tree.insert(5)
tree.insert(7)
tree.insert(6)
tree.preTravel(tree.root)
print(‘\n‘)
tree.middleTravel(tree.root)
print(‘\n‘)
tree.backTravel(tree.root)
print(‘\n‘)

二叉树