BFS of Tree: Implementation Steps for Breadth-First Search and Level Order Traversal

BFS is a classic tree traversal method that accesses nodes in a "breadth-first" (level order) manner, with its core implementation relying on a queue (FIFO). The steps are as follows: initialize the queue by enqueueing the root node, then repeatedly dequeue the front node for access, enqueue its left and right children (in natural order) until the queue is empty. BFS is suitable for tree hierarchy problems, such as calculating tree height, determining a perfect binary tree, and finding the shortest root-to-leaf path. For the binary tree `1(2(4,5),3)`, the level order traversal sequence is 1→2→3→4→5. Key points: The queue ensures level order, the enqueue order of children (left→right), time complexity O(n) (where n is the number of nodes), and space complexity O(n) (worst-case scenario with n/2 nodes in the queue). Mastering BFS enables efficient solution of level-related problems and serves as a foundation for more complex algorithms.