ally.clj

(defn ally? [board point color] (= color (nth board point)))

(defn new-ally? [board point color ally]
  (and (ally? board point color) (not (.contains ally point))))

(defn find-neighbors [point size]
  (let [north (- point size)
        east  (inc point)
        south (+ point size)
        west  (dec point)]
    (filter #(not (out-of-bound % size)) '(north east south west))))

(defn find-ally-recursive [board point color ally size]
  (let [ally (cons point ally) neighbors (find-neighbors point size)]
    (reduce
      #(if (new-ally? board %2 color %1)                 ; if point is a new ally
           (find-ally-recursive board %2 color %1 size)  ; then continue to explore the next neighbor
           %1)                                           ; else return ally group
        ally neighbors)))                                ; %1 = ally group, %2 = neighbors

(defn find-ally-group [board point color size]
  {:color color :points (find-ally-recursive board point color () size)})