Boundary Traversal of Binary Tree

Given a binary tree of integers, your task is to print the boundary nodes of the binary tree in an anti-clockwise direction starting from the root node.

Note:

The boundary includes nodes from the left boundary, leaf nodes, and the right boundary in sequence. Only unique nodes should be included in the output.

Input:

The input consists of multiple test cases. The first line contains an integer ‘T’ representing the number of test cases. Subsequent lines describe each test case in level-order form, with node values separated by spaces. Use -1 to denote null nodes.

Example:

For example, consider the binary tree input:
1
2 3
4 -1 5 6
-1 7 -1 -1 -1 -1
-1 -1

Input for the tree is: 1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -1

Output:

For each test case, print the boundary nodes of the binary tree separated by single spaces. Output for each test case is on a separate line.

Constraints:

• 1 ≤ T ≤ 10²
• 1 ≤ N ≤ 2¹²
• Time Limit: 1 sec

Note:

Implement the function to calculate the boundary traversal. The printing of the result is handled separately.