Implementing breadth-first or level-order traversal using a queue.
Breadth-First Search (BFS), also known as Level-Order Traversal, is another way to visit all nodes in a tree. Unlike DFS which goes deep, BFS explores the tree layer by layer. It visits all nodes at the current depth before moving on to the nodes at the next depth level. This traversal cannot be easily implemented with recursion; instead, it uses a queue data structure. The algorithm is as follows: 1. Create an empty queue. 2. Add the root node to the queue. 3. Loop as long as the queue is not empty: a. Dequeue a node from the front of the queue. b. Visit (e.g., print) the dequeued node. c. Enqueue the left child of the node, if it exists. d. Enqueue the right child of the node, if it exists. This process guarantees that nodes are visited in the order of their level. BFS is particularly useful for finding the shortest path between two nodes in an unweighted graph (a tree is a type of graph). It's also the basis for solving problems like finding the maximum width of a tree or printing the 'view' of a tree from one side.