class Solution:
def findTarget(self, root: TreeNode, k: int) -> bool:
s = set() #记录访问过的节点值
q = [root]
while q:
for _ in range(len(q)):
node = q.pop(0)
val = node.val
if k - val in s:
return True
s.add(val)
if node.left:
q.append(node.left)
if node.right:
q.append(node.right)
return False