Duplicate Subtrees Problem Statement

Given a binary tree, return the root values of all duplicate subtrees. Two subtrees are considered duplicate if they have the same structure with identical node values. For each duplicate subtree, return the root value of any one of them.

Example:

Tree:

 Consider the following binary tree:  

Output:

{2, 3}

Explanation:

The duplicate subtrees are {{2, 3}, {3}}, hence the root values are {2, 3}. The order doesn't matter.

Input:

T, then each test case with nodes in level order, using -1 for null nodes.
Example for one tree: 1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -1

Output:

Space-separated root values of all duplicate subtrees for each test case in separate lines. Use -1 if no duplicates.

Constraints:

• 1 <= T <= 5
• 1 <= N <= 100
• 1 <= val <= 10⁵
• Time Limit: 1 sec

Note:

The input for the tree is given as a single sequence of space-separated values.