Boundary Traversal of Binary Tree Problem Statement

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

Note:

The boundary nodes comprise the left boundary, right boundary, and all the leaf nodes, without including any duplicates. Even if the node values are duplicates, include them only once.

Input:

'T' which denotes the number of test cases followed by binary tree nodes in level order. Use '-1' to represent null nodes. The input is a single line of node values separated by spaces.

Output:

Print the boundary nodes for each test case, separated by spaces, each test case on a new line.

Example:

Input:

1
1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -1

Output:

1 2 4 7 5 6 3

Explanation:

The binary tree level order input describes the tree as follows -

Level 1: Root node is 1
Level 2: Left child of 1 is 2, Right child is 3
Level 3: Left child of 2 is 4, Right child is null
......
Boundary order: 1 -> 2 -> 4 -> 7 (leaf nodes) -> 5 -> 6 -> 3

Constraints:

• 1 ≤ T ≤ 102
• 1 ≤ N ≤ 212 (where 'N' is the total number of nodes)
• Time Limit: 1 sec