Pair Sum in Binary Search Tree

Given a Binary Search Tree (BST) and a target value 'K', determine if there exist two unique elements in the BST such that their sum equals the target 'K'.

Explanation:

A BST is a type of binary tree where each node has a maximum of two children, and it satisfies the following properties:

• The left subtree of a node contains only nodes with values less than the node's value.
• The right subtree of a node contains only nodes with values greater than the node's value.
• Both the left and right subtrees must also be BSTs.

Input:

The first line contains an integer ‘T’, representing the number of test cases. For each test case:
- The first line provides elements of the BST in level order, with '-1' denoting null nodes.
- The second line gives the integer ‘K’, the target sum value.

Output:

For each test case, output a single line containing 'true' or 'false'.

Example:

Input:  
20 10 35 5 15 30 42 -1 13 -1 -1 -1 -1 -1 -1 -1
K = 45
Output:
true

Constraints:

• 1 <= T <= 5
• 1 <= N <= 10^3
• 0 <= DATA <= 10^9
• 1 <= K <= 10^9

Note:

The input for the tree should be a single line with values separated by spaces. Null nodes are represented as '-1'. Implement the function and logic, as output handling is already managed.