Given the root of a binary search tree and an integer k, return trueif there exist two elements in the BST such that their sum is equal tok, orfalseotherwise.
Example 1:
Input: root = [5,3,6,2,4,null,7], k = 9
Output: true
Example 2:
Input: root = [5,3,6,2,4,null,7], k = 28
Output: false
Constraints:
The number of nodes in the tree is in the range [1, 104].
-104 <= Node.val <= 104
root is guaranteed to be a valid binary search tree.