**Prerequisites :-** Binary Trees, Level Order Traversal.

**Problem :-** Given a level order traversal of a complete binary tree which has N nodes numbered from 1 to N. The label of the i-th node in the traversal is Ai. You need to reconstruct that tree.

**Solution Approach :-** We can use a level order traversal approach to reconstruct the binary tree. It utilizes a queue to keep track of the nodes and their children during the reconstruction process.

A more detailed explanation of the *reconstruct()* function:

- The function initializes a queue and the root of the binary tree using the first element of the traversal array.
- It then iterates through the remaining elements of the array.
- For each element, it creates a new node with the value from the traversal array and assigns it as the left child of the current node (if the value is not -1).
- If there are more elements in the traversal array, it repeats the process for the right child.
- The queue helps in keeping track of the nodes and their children during the reconstruction process.

**Time Complexity:** The time complexity of this solution is O(N), where N is the number of nodes in the binary tree. The function processes each element in the level order traversal array once.

**Space Complexity:** The space complexity is O(N), where N is the number of nodes in the binary tree. This is due to the space required for the queue, which can have at most N/2 nodes in a complete binary tree. The new nodes created during the reconstruction also contribute to the space complexity.