写出非递归的方法实现对给定二叉树的先序和层序遍历算法,并给出一组数据

非递归的先序遍历算法：

def preorderTraversal(root):
    if not root:
        return []
    stack = [root]
    res = []
    while stack:
        node = stack.pop()
        res.append(node.val)
        if node.right:
            stack.append(node.right)
        if node.left:
            stack.append(node.left)
    return res

非递归的层序遍历算法：

def levelOrderTraversal(root):
    if not root:
        return []
    queue = [root]
    res = []
    while queue:
        level = []
        for i in range(len(queue)):
            node = queue.pop(0)
            level.append(node.val)
            if node.left:
                queue.append(node.left)
            if node.right:
                queue.append(node.right)
        res.append(level)
    return res

数据示例：

# 先构造一棵二叉树
#       1
#      / \
#     2   3
#    / \   \
#   4   5   6
from collections import deque

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
root.left.left = TreeNode(4)
root.left.right = TreeNode(5)
root.right.right = TreeNode(6)

# 先序遍历输出：[1, 2, 4, 5, 3, 6]
print(preorderTraversal(root))

# 层序遍历输出：[[1], [2, 3], [4, 5, 6]]
print(levelOrderTraversal(root))