利用先序序列建立二叉树，并输出先序、中序和后序序列,，使用非递归

以下是利用先序序列建立二叉树，并输出先序、中序和后序序列的非递归实现代码：

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

def buildTree(preorder):
    if not preorder:
        return None
    
    root = TreeNode(preorder[0])
    stack = [root]
    i = 1
    
    while i < len(preorder):
        node = TreeNode(preorder[i])
        if node.val < stack[-1].val:
            stack[-1].left = node
        else:
            while stack and node.val > stack[-1].val:
                temp = stack.pop()
            temp.right = node
        stack.append(node)
        i += 1
    
    return root

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

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

def postorderTraversal(root):
    if not root:
        return []
    
    stack = [root]
    res = []
    
    while stack:
        node = stack.pop()
        res.append(node.val)
        
        if node.left:
            stack.append(node.left)
        if node.right:
            stack.append(node.right)
    
    return res[::-1]

其中，`buildTree`函数用于根据先序序列建立二叉树，`inorderTraversal`、`preorderTraversal`和`postorderTraversal`函数分别用于输出中序、先序和后序序列。这里使用了栈来辅助实现非递归遍历。