Level Order Traversal.

Level Order Traversal, also known as Breadth First Search (BFS), is a technique to traverse all nodes in a binary tree level by level. This approach ensures that nodes at the same level are visited before those at the next level. The traversal can be implemented in two main ways: using recursion with a stack or iteratively with a queue.

In the recursive approach, a helper function is used to traverse the tree, passing the current node and its level. Nodes at the same level are grouped together in a result array, where the index corresponds to the level of the node. On the other hand, the iterative approach uses a queue to process the nodes level by level. Starting from the root, the left and right children of each node are enqueued for processing. This method maintains a First-In-First-Out (FIFO) order, ensuring that all nodes at the current level are processed before moving to the next level. Both approaches have a time and space complexity of O(n), where n is the number of nodes in the tree.

For more details, please go through - Level Order Traversal (Breadth First Search or BFS) of Binary Tree