Level Order Traversal of a Binary Tree

To solve the Level Order Traversal, I would use a Breadth-First Search approach leveraging a standard Queue data structure. First, I check if the root is null; if so, I return an empty list immediately. Otherwise, I initialize a queue and add the root node. Then, I enter a while loop that continues as long as the queue has elements. Inside the loop, I capture the current queue size, which represents the number of nodes at the current level. I iterate exactly that many times to process only the nodes at this specific depth. During each iteration, I dequeue a node, append its value to a temporary level list, and enqueue its left and right children if they exist. After processing all nodes in the current level, I add the temporary level list to my final result. For example, given a tree with root 3, left child 9, and right child 20 (with 20 having children 15 and 7), the first iteration yields [3], the second [9, 20], and the third [15, 7]. This ensures strict left-to-right ordering per level. The time complexity is O(N) since we visit every node once, and space complexity is O(W) for the queue, where W is the maximum width of the tree. This approach aligns well with Amazon's focus on efficient, scalable algorithms for handling hierarchical data structures.