Checking the existence of a pair of nodes with sum k in a binary search tree

Given a binary search tree (BST) and an integer k. Determine whether there are two distinct nodes in the tree such that their values sum up to k.

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 total number of nodes is in the range from 1 to 10^4.
• Node values are in the range from -10^4 to 10^4.
• The tree is guaranteed to be a valid BST.
• The value of k is in the range from -10^5 to 10^5.

public class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;

    TreeNode() {}

    TreeNode(int val) {
        this.val = val;
    }

    TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}

class Solution {
    public boolean findTarget(TreeNode root, int k) {
        // Implement logic to find if two elements in BST sum up to k
    }
}