已知一棵二叉树的前序遍历序列为ABCDEF，中序遍历序列为CBDAEF，请还原这棵二叉树？这棵二叉树的后序遍历结果是多少

已知一棵二叉树的前序遍历序列为ABCDEF，中序遍历序列为CBDAEF，可以还原出如下的二叉树：

       A
     /   \
    B     E
   / \     \
  C   D     F

该二叉树的后序遍历序列为：CDCBFEA。

下面是Python代码实现：

# 定义二叉树节点类
class TreeNode:
    def __init__(self, val=0):
        self.val = val
        self.left = None
        self.right = None
        
# 根据前序遍历序列和中序遍历序列还原二叉树
def buildTree(preorder, inorder):
    if not preorder or not inorder:
        return None
    
    root_val = preorder[0]
    root = TreeNode(root_val)
    mid = inorder.index(root_val)
    
    root.left = buildTree(preorder[1:mid+1], inorder[:mid])
    root.right = buildTree(preorder[mid+1:], inorder[mid+1:])
    
    return root

# 后序遍历二叉树
def postorderTraversal(root):
    if not root:
        return []
    
    res = []
    stack = [(root, False)]
    while stack:
        node, visited = stack.pop()
        if not node:
            continue
        
        if visited:
            res.append(node.val)
        else:
            stack.append((node, True))
            stack.append((node.right, False))
            stack.append((node.left, False))
    
    return res

# 测试
preorder = ['A', 'B', 'C', 'D', 'E', 'F']
inorder = ['C', 'B', 'D', 'A', 'E', 'F']
root = buildTree(preorder, inorder)
print(postorderTraversal(root))  # ['C', 'D', 'B', 'F', 'E', 'A']