创建二叉树和三种遍历

二叉树

创建和遍历

# -*- coding:utf-8 -*-
class TreeNode:
    def __init__(self, x, left=None, right=None):
        self.val = x
        self.left = left
        self.right = right

    @staticmethod
    def before(self):
        """
        前序遍历 根 左 右
        :param self:
        :return:
        """
        if not self:
            return
        print(self.val)
        self.before(self.left)
        self.before(self.right)

    @staticmethod
    def middle(self):
        """
        中序遍历,左  根  右
        :param self:
        :return:
        """
        if not self:
            return
        self.middle(self.left)
        print(self.val)
        self.middle(self.right)

    @staticmethod
    def after(self):
        """
        右序遍历 左  右  根
        :param self:
        :return:
        """
        if not self:
            return
        self.after(self.left)
        self.after(self.right)
        print(self.val)
    
        @staticmethod
    def depth(self):
        """
        层次遍历
        :return:
        """
        if not self:
            return
        res, q = [],[]
        # 根节点入队
        q.append(self)
        # 循环 q 队列
        while q:
            # 取出第一个元素
            node = q.pop(0)
            # 把节点的值加到列表
            res.append(node.val)
            # 如果节点的左边有节点，入队
            if node.left:
                q.append(node.left)
            # 如果节点的右边有节点，入队
            if node.right:
                q.append(node.right)
        return res

    def __str__(self):
        return self.val


root = TreeNode(
    'A',
    TreeNode('B',
             TreeNode('D',
                      TreeNode('G')),
             ),
    TreeNode('C',
             TreeNode('E',
                      TreeNode('H')),
             TreeNode('F',
                      right=TreeNode('I'))
             )
)
# 验证
# print(root)
# print(root.left)
# print(root.right)
# print(root.left.left)
# print(root.right.left)

# root.before(root)
# root.middle(root)
root.after(root)
print(root.depth(root))