# coding:utf-8

class Node(object):
    """节点"""

    def __init__(self, item):
        self.elem = item
        self.lchild = None
        self.rchild = None


class Tree(object):
    """二叉树"""
    # 初始化一个节点
    def __init__(self):
        self.root = None

    # 为树添加节点
    def add(self, item):
        node = Node(item)
        # 如果树是空的，则对根节点赋值
        if self.root is None:
            self.root = node
            return
        # 加入根节点
        queue = [self.root]
        # 对已有的节点进行层次遍历
        while queue:
            # 弹出当前处理节点元素
            cur_node = queue.pop(0)
            # 判断当前节点左孩子是否为空
            if cur_node.lchild is None:
                cur_node.lchild = node
                return
            else:
                queue.append(cur_node.lchild)
            if cur_node.rchild is None:
                cur_node.rchild = node
                return
            else:
                queue.append(cur_node.rchild)


    def breadth_travel(self):
        """广度遍历(层次遍历)"""
        if self.root is None:
            return
        queue = [self.root]
        while queue:
            cur_node = queue.pop(0)
            print(cur_node.elem, end=" ")
            if cur_node.lchild is not None:
                queue.append(cur_node.lchild)
            if cur_node.rchild is not None:
                queue.append(cur_node.rchild)

    def preorder(self, node):
        """先序遍历(根左右)"""
        if node is None:
            return
        print(node.elem, end=" ")
        self.preorder(node.lchild)
        self.preorder(node.rchild)

    def inorder(self, node):
        """中序遍历(左根右)"""
        if node is None:
            return
        self.inorder(node.lchild)
        print(node.elem, end=" ")
        self.inorder(node.rchild)

    def postorder(self, node):
        """后序遍历(左右根)"""
        if node is None:
            return
        self.postorder(node.lchild)
        self.postorder(node.rchild)
        print(node.elem, end=" ")


if __name__ == "__main__":
    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.breadth_travel()
    print(" ")
    tree.preorder(tree.root)
    print(" ")
    tree.inorder(tree.root)
    print(" ")
    tree.postorder(tree.root)
    print(" ")