题目链接：1022. 从根到叶的二进制数之和
深度遍历二叉树，记录一个状态，表示已经积累的和。
# 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:
def sumRootToLeaf(self, root: TreeNode | None) -> int:
if not root:
return 0
def visit(node: TreeNode, acc: int) -> int:
acc = (acc << 1) | node.val
if not node.left and not node.right:
return acc
ans = 0
if node.left:
ans += visit(node.left, acc)
if node.right:
ans += visit(node.right, acc)
return ans
return visit(root, 0)