欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  IT编程

python数据结构之二叉树的统计与转换实例

程序员文章站 2022-06-30 11:10:22
一、获取二叉树的深度就是二叉树最后的层次,如下图: 实现代码:复制代码 代码如下:def getheight(self):    ...

一、获取二叉树的深度

就是二叉树最后的层次,如下图:

python数据结构之二叉树的统计与转换实例

实现代码:

复制代码 代码如下:

def getheight(self):
        ''' 获取二叉树深度 '''
        return self.__get_tree_height(self.root)

    def __get_tree_height(self, root):
        if root is 0:
            return 0
        if root.left is 0 and root.right is 0:
            return 1
        else:
            left = self.__get_tree_height(root.left)
            right = self.__get_tree_height(root.right)
            if left < right:
                return right + 1
            else:
                return left + 1

二、叶子的统计

叶子就是二叉树的节点的 left 指针和 right 指针分别指向空的节点

复制代码 代码如下:

def getleafcount(self):
        ''' 获取二叉树叶子数 '''
        return self.__count_leaf_node(self.root)

    def __count_leaf_node(self, root):
        res = 0
        if root is 0:
            return res
        if root.left is 0 and root.right is 0:
            res += 1
            return res
        if root.left is not 0:
            res += self.__count_leaf_node(root.left)
        if root.right is not 0:
            res += self.__count_leaf_node(root.right)
        return res

三、统计叶子的分支节点

与叶子节点相对的其他节点 left 和 right 的指针指向其他节点

复制代码 代码如下:

def getbranchcount(self):
        ''' 获取二叉树分支节点数 '''
        return self.__get_branch_node(self.root)

    def __get_branch_node(self, root):
        if root is 0:
            return 0
        if root.left is 0 and root.right is 0:
            return 0
        else:
            return 1 + self.__get_branch_node(root.left) + self.__get_branch_node(root.right)

四、二叉树左右树互换

复制代码 代码如下:

def replacelem(self):
        ''' 二叉树所有结点的左右子树相互交换 '''
        self.__replace_element(self.root)

    def __replace_element(self, root):
        if root is 0:
            return
        root.left, root.right = root.right, root.left
        self.__replace_element(root.left)
        self.__replace_element(root.right)

这些方法和操作,都是运用递归。其实二叉树的定义也是一种递归。附上最后的完整代码:

复制代码 代码如下:

# -*- coding: utf - 8 - *-

    
class treenode(object):

    def __init__(self, left=0, right=0, data=0):
        self.left = left
        self.right = right
        self.data = data

    
class binarytree(object):

    def __init__(self, root=0):
        self.root = root

    def is_empty(self):
        if self.root is 0:
            return true
        else:
            return false

    def create(self):
        temp = input('enter a value:')
        if temp is '#':
            return 0
        treenode = treenode(data=temp)
        if self.root is 0:
            self.root = treenode

        treenode.left = self.create()
        treenode.right = self.create()

    def preorder(self, treenode):
        '前序(pre-order,nlr)遍历'
        if treenode is 0:
            return
        print treenode.data
        self.preorder(treenode.left)
        self.preorder(treenode.right)

    def inorder(self, treenode):
        '中序(in-order,lnr'
        if treenode is 0:
            return
        self.inorder(treenode.left)
        print treenode.data
        self.inorder(treenode.right)

    def postorder(self, treenode):
        '后序(post-order,lrn)遍历'
        if treenode is 0:
            return
        self.postorder(treenode.left)
        self.postorder(treenode.right)
        print treenode.data

    def preorders(self, treenode):
        '前序(pre-order,nlr)非递归遍历'
        stack = []
        while treenode or stack:
            if treenode is not 0:
                print treenode.data
                stack.append(treenode)
                treenode = treenode.left
            else:
                treenode = stack.pop()
                treenode = treenode.right

    def inorders(self, treenode):
        '中序(in-order,lnr) 非递归遍历'
        stack = []
        while treenode or stack:
            if treenode:
                stack.append(treenode)
                treenode = treenode.left
            else:
                treenode = stack.pop()
                print treenode.data
                treenode = treenode.right

    def postorders(self, treenode):
        '后序(post-order,lrn)非递归遍历'
        stack = []
        pre = 0
        while treenode or stack:
            if treenode:
                stack.append(treenode)
                treenode = treenode.left
            elif stack[-1].right != pre:
                treenode = stack[-1].right
                pre = 0
            else:
                pre = stack.pop()
                print pre.data

    # def postorders(self, treenode):
    #     '后序(post-order,lrn)非递归遍历'
    #     stack = []
    #     queue = []
    #     queue.append(treenode)
    #     while queue:
    #         treenode = queue.pop()
    #         if treenode.left:
    #             queue.append(treenode.left)
    #         if treenode.right:
    #             queue.append(treenode.right)
    #         stack.append(treenode)
    #     while stack:
    #         print stack.pop().data

    def levelorders(self, treenode):
        '层序(post-order,lrn)非递归遍历'
        from collections import deque
        if not treenode:
            return
        q = deque([treenode])
        while q:
            treenode = q.popleft()
            print treenode.data
            if treenode.left:
                q.append(treenode.left)
            if treenode.right:
                q.append(treenode.right)

    def getheight(self):
        ''' 获取二叉树深度 '''
        return self.__get_tree_height(self.root)

    def __get_tree_height(self, root):
        if root is 0:
            return 0
        if root.left is 0 and root.right is 0:
            return 1
        else:
            left = self.__get_tree_height(root.left)
            right = self.__get_tree_height(root.right)
            if left < right:
                return right + 1
            else:
                return left + 1

    def getleafcount(self):
        ''' 获取二叉树叶子数 '''
        return self.__count_leaf_node(self.root)

    def __count_leaf_node(self, root):
        res = 0
        if root is 0:
            return res
        if root.left is 0 and root.right is 0:
            res += 1
            return res
        if root.left is not 0:
            res += self.__count_leaf_node(root.left)
        if root.right is not 0:
            res += self.__count_leaf_node(root.right)
        return res

    def getbranchcount(self):
        ''' 获取二叉树分支节点数 '''
        return self.__get_branch_node(self.root)

    def __get_branch_node(self, root):
        if root is 0:
            return 0
        if root.left is 0 and root.right is 0:
            return 0
        else:
            return 1 + self.__get_branch_node(root.left) + self.__get_branch_node(root.right)

    def replacelem(self):
        ''' 二叉树所有结点的左右子树相互交换 '''
        self.__replace_element(self.root)

    def __replace_element(self, root):
        if root is 0:
            return
        root.left, root.right = root.right, root.left
        self.__replace_element(root.left)
        self.__replace_element(root.right)

node1 = treenode(data=1)
node2 = treenode(node1, 0, 2)
node3 = treenode(data=3)
node4 = treenode(data=4)
node5 = treenode(node3, node4, 5)
node6 = treenode(node2, node5, 6)
node7 = treenode(node6, 0, 7)
node8 = treenode(data=8)
root = treenode(node7, node8, 'root')

    
bt = binarytree(root)

print u'''

生成的二叉树

------------------------
         root
      7        8
    6
  2   5
1    3 4

-------------------------

'''