iterative pre order in order post order

   def postorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
        if not root:
            return []
        s=[root]
        res=[]
        while s:
            t=s.pop()
            if t.left:
                s.append(t.left)
            if t.right:
                s.append(t.right)
            res.append(t.val)
        return res[::-1]

Inorder:
    def InOrder(self,root):
        ans,st=[],[]
        cur=root
        while cur or st:
            if cur==None:
                cur=st.pop()
                ans.append(cur.data)
                cur=cur.right
            else:
                st.append(cur)
                cur=cur.left
        return ans

def preorder(root):
    res,st=[],[]
    cur=root
    while st or cur:
        if cur==None:
            cur=st.pop()
            cur=cur.right
        else:
            res.append(cur.data)
            st.append(cur)
            cur=cur.left
    return res