python实现二叉树广度优先遍历，先序遍历，中序遍历，后续遍历

# 二叉树广度优先遍历
class Node():
    def __init__(self, item):
        self.item = item
        self.lchild = None
        self.rchild = None


class BinaryTree():
    def __init__(self, node=None):
        self.root = node

    def add(self, item):
        if self.root is None:
            self.root = Node(item)
        else:
            queue = []
            queue.append(self.root)

            while len(queue) > 0:
                node = queue.pop(0)
                if not node.lchild:
                    node.lchild = Node(item)
                    return
                else:
                    queue.append(node.lchild)
                if not node.rchild:
                    node.rchild = Node(item)
                    return
                else:
                    queue.append(node.rchild)
    def breadh_travel(self):
        if self.root is None:
            return
        queue = []
        queue.append(self.root)
        while len(queue) >0:
            node = queue.pop(0)
            print(node.item,end=" ")
            if node.lchild:
                queue.append(node.lchild)
            if node.rchild:
                queue.append(node.rchild)
    def preorder_travel(self,root):
        """先序遍历，顺序是：根 左 右"""
        if root:
            print(root.item,end=" ")
            self.preorder_travel(root.lchild)
            self.preorder_travel(root.rchild)
    def inorder_travel(self,root):
        """中序遍历，顺序是：左 根 右"""
        if root:
            self.inorder_travel(root.lchild)
            print(root.item,end=" ")
            self.inorder_travel(root.rchild)
    def postorder_travel(self,root):
        """后序遍历，顺序是：左 右 根"""
        if root:
            self.postorder_travel(root.lchild)
            self.postorder_travel(root.rchild)
            print(root.item,end=" ")




if __name__ == '__main__':
    tree = BinaryTree()
    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.breadh_travel()
    print("")
    tree.preorder_travel(tree.root)
    print("")
    tree.inorder_travel(tree.root)
    print("")
    tree.postorder_travel(tree.root)
    print("")

结果：