question 3b success

clojure/src/question_3.clj

@@ -9,19 +9,44 @@
         lines (strings/split-lines input)] ;(mapv Integer/parseInt))]
     (mapv parse-line lines)))
 
-(defn all-possible-joltages [line]
+(defn all-possible-two-joltages [line]
   (let [n (count line)]
     (for [s (range n)
           e (range (inc s) n)]
-      ;[s e]
       (+ (* 10 (get line s))  (get line e)))))
 
-
-(defn line-joltage [line]
-  (apply max (all-possible-joltages line)))
+(defn line-two-joltage [line]
+  (apply max (all-possible-two-joltages line)))
 
 (defn question-3-a [document]
-  (reduce + (map line-joltage (parse-input document))))
+  (reduce + (map line-two-joltage (parse-input document))))
+
+(defn first-max-with-index [lst]
+  (let [max-value (volatile! -1)
+        max-index (volatile! -1)]
+    (when (seq lst)
+      (loop [[h & rest] lst
+             idx 0]
+        (when (> h @max-value)
+          (vreset! max-value h)
+          (vreset! max-index idx))
+        (when (seq rest)
+          (recur rest (inc idx)))))
+    [@max-index @max-value]))
+
+(defn pow [x n]
+  (reduce *' (repeat n x)))
+
+(defn line-n-joltage [line n]
+  (if (zero? n)
+    0
+    (let [[idx val] (first-max-with-index (drop-last (dec n) line))]
+      (+ (* (pow 10 (dec n)) val)
+         (line-n-joltage (drop (inc idx) line) (dec n))))))
+
+(defn question-3-b [document]
+  (reduce + (map #(line-n-joltage % 12) (parse-input document))))
 
 (defn -main [& args]
-  (println "Solution to question 3-a is: " (question-3-a inputs/question-3)))
+  (println "Solution to question 3-a is: " (question-3-a inputs/question-3))
+  (println "Solution to question 3-b is: " (question-3-b inputs/question-3)))