九.二叉树

回顾:

链表：
数据结构的封装：
节点： class Node():
 def __init__(self,item):
     self.item = item
     self.next = None
链表： class Link():
  def __init__(self):
     self._head = None

今日内容:

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('
')
tree.backTravel(tree.root)
print('
')
tree.middleTravel(tree.root)
print('
')

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('
')
tree.middleTravel(tree.root)
print('
')
tree.backTravel(tree.root)
print('
')