graphs.clj

(defn breadth-first-traversal
  ([g start]
     (breadth-first-traversal g [start] [[] #{}]))
  ([g queue [path visited]]
     (if (seq queue)
       (let [node (first queue)
             next (remove visited (neighbors g node))]
         (lazy-seq (breadth-first-traversal g (into (subvec queue 1) next)
                                            [(conj path node)
                                             (into (conj visited node) next)])))
       path)))

(defn breadth-first-traversal
  ([g start]
     (breadth-first-traversal g [start] #{}))
  ([g queue visited]
     (lazy-seq
     (if (seq queue)
       (let [node (first queue)
             next (remove visited (neighbors g node))]
         (cons node (breadth-first-traversal g (into (subvec queue 1) next)
                                             (into (conj visited node) next))))))))