Breadth-first search, often abbreviated BFS, is another way to search a graph. Unlike depth-first search, breadth-first search does not use recursion. Instead, the algorithm revolves around our old friend, the queue. As you’ll recall, the queue is a FIFO data structure, and whatever goes in first, comes out first.

Here is the algorithm for breadth-first search. As with our walkthrough of depth-first search, we’re going to focus on graph traversal using breadth-first search. That is, we’re going to visit each vertex from our example social network.

Here is the algorithm for breadth-first traversal:

  1. Start at any vertex within the graph. We’ll call this the “starting vertex.”

  2. Add the starting vertex to the hash table to mark ...

Get A Common-Sense Guide to Data Structures and Algorithms, Second Edition, 2nd Edition now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.