653) Two Sum IV - Input is a BST.py

class Solution:
    def findTarget(self, root: Optional[TreeNode], k: int) -> bool:
        l = set()
        def dfs(node):
            if not node:return False
            y = k -node.val
            if y in l:
                return True
            else:
                l.add(node.val)
            return dfs(node.left) or dfs(node.right)
        return dfs(root)