653. Two Sum IV - Input is a BST

653. Two Sum IV - Input is a BST

很简单的题，可以深度优先，也可广度优先。

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def findTarget(self, root, k):
        """
        :type root: TreeNode
        :type k: int
        :rtype: bool
        """
        myset = set()
        qu = [root]
        while qu:
            node = qu.pop(0)
            if k - node.val in myset:
                return True
            else:
                myset.add(node.val)
            if node.left:
                qu.append(node.left)
            if node.right:
                qu.append(node.right)
        return False