Given a Binary Search Tree and a target number, return true if there exist two elements in the BST such that their sum is equal to the given target.

Example 1:

Input:     5   / \  3   6 / \   \2   4   7Target = 9Output: True

 

Example 2:

Input:     5   / \  3   6 / \   \2   4   7Target = 28Output: False 思路：递归遍历BST（Binary Search Tree）

class Solution:    def findTarget(self, root, k):        """        :type root: TreeNode        :type k: int        :rtype: bool        """        self.root = root        self.k = k        return self.searchNumber(root)            def searchNumber(self, root):        if not root:            return False        node = self.root        n = self.k - root.val        if n != root.val:            while node:                if node.val == n:                    return True                if n > node.val:                    node = node.right                else:                    node = node.left        return self.searchNumber(root.left) or self.searchNumber(root.right)