I feel like it&#x27;s a little weird that one of the author&#x27;s big examples of a difficult algorithmic question is breadth-first search.  While I agree it&#x27;s not something that&#x27;s very likely to come up much in real work (especially for a front-end dev!), it&#x27;s also...  not actually hard?  You check the current node for your truth condition, you add its children to a queue, you pop the queue and do the same thing for that node.  If the queue is empty, you return false.