LC1022 Sum of Root To Leaf Binary Numbers

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
#time O(N) space O(H) H:since the stack for recursion
    def sumRootToLeaf(self, root: TreeNode) -> int:
        self.res = 0
        self.preorder(root,0)
        return self.res 
    
    def preorder(self,node,cur):
        if node:
            cur = (cur*2) | node.val
            if not( node.left or node.right):
                self.res  += cur 

            self.preorder(node.left, cur)
            self.preorder(node.right, cur)