Stumped with functional breadth-first tree traversal in Clojure?

Question

Say I have a tree defined as per the recommendation in this post, although it\'s a vector in my case, which hopefully shouldn\'t matter (they\'re vectors in Programming Clojure

Answer 1

many combinations of reduceand conj can be replaced with single into call in the case above with reduce you may need to pass an initial empty vector to reduce to get make conjunction happy.