【694】Python实现二叉树

参考：二叉树的创建及遍历(Python版)

几种遍历方式解读，所谓顺序就是根节点出现的位置！

• 先序遍历：中左右

• 中序遍历：左中右

• 后序遍历：左右中

代码如下：

class BTNode(object):
    def __init__(self, key=None, lchild=None, rchild=None):
        self.key = key
        self.lchild = lchild
        self.rchild = rchild

class BiTree(object):
    def __init__(self, data_list):
        #初始化即将传入的列表的迭代器
        self.it = iter(data_list)

    def createBiTree(self, bt=None):    
        try:
            #步进获取下一个元素
            next_data = next(self.it)
            #如果当前列表元素为'#', 则认为其为 None
            if next_data == "#":
                bt = None
            else:
                bt = BTNode(next_data)
                bt.lchild = self.createBiTree(bt.lchild)
                bt.rchild = self.createBiTree(bt.rchild)
        except Exception as e:
            print(e)

        return bt
    
    #先序遍历函数
    def preOrderTrave(self, bt):
        if bt is not None:
            print(bt.key, end=" ")
            self.preOrderTrave(bt.lchild)
            self.preOrderTrave(bt.rchild)

    #中序遍历函数
    def inOrderTrave(self, bt):
        if bt is not None:
            self.inOrderTrave(bt.lchild)
            print(bt.key, end=" ")
            self.inOrderTrave(bt.rchild)

    #后序遍历函数
    def postOrderTrave(self, bt):
        if bt is not None:
            self.postOrderTrave(bt.lchild)
            self.postOrderTrave(bt.rchild)
            print(bt.key, end=" ")

    #综合打印
    def printTrave(self, bt):
        print("先序遍历: ", end="")
        self.preOrderTrave(bt)
        print('\n')
        print("中序遍历: ", end="")
        self.inOrderTrave(bt)
        print('\n')
        print("后序遍历: ", end="")
        self.postOrderTrave(bt)
        print('\n')


data = input("Please input the node value: ")
data_list = list(data)

btree = BiTree(data_list)
root = btree.createBiTree()
btree.printTrave(root)