day 3

src/day3.clj

@@ -0,0 +1,73 @@
+(ns day3
+  (:require [clojure.edn :as edn]
+            [clojure.string :as string]
+            [helpers :refer [get-input]]))
+
+
+(def test-input "987654321111111
+811111111111119
+234234234234278
+818181911112111
+")
+
+(defn- max-joltage [bank]
+  (let [bank (->> bank string/trim (map str))
+        joltages
+        (loop [r [] bank bank]
+          (if (= 1 (count bank))
+            r
+            (recur
+             (into r (mapv (partial str (first bank)) (rest bank)))
+             (rest bank))))]
+    (->> (sort joltages)
+         last
+         Integer/parseInt)))
+
+;;(def input (string/split-lines test-input))
+(def input (string/split-lines (get-input 3)))
+
+(println "Total output joltage:"
+         (->>
+          input
+          (map max-joltage)
+          (reduce +)))
+
+(defn- max-with-tail
+  [bank n]
+  (loop [r [[(first bank) (rest bank)]]
+         bank (rest bank)]
+    (if (> n (count bank))
+      r
+      (let [c (first bank)
+            m (-> r first first)
+            bank (rest bank)]
+        (cond
+          (= c m)
+          (recur (conj r [c bank]) bank)
+          (> c m)
+          (recur [[c bank]] bank)
+          (< c m)
+          (recur r bank))))))
+
+(defn- len [n]
+  (-> n str count))
+
+(defn- next-j [[j bank]]
+  (let [r (max-with-tail bank (- 12 (len j)))]
+    (mapv #(vector (+ (* 10 j) (first %)) (second %)) r)))
+
+(defn- max-joltage-12 [bank]
+  (let [bank (map (comp Integer/parseInt str) bank)]
+    (->>
+     (loop [r (max-with-tail bank 12)]
+       (if (= 12 (-> r first first len))
+         r
+         (recur (mapcat next-j r))))
+     (map first)
+     (apply max))))
+
+(println
+ "Total output joltage for 12 batteries:"
+ (->>
+  (map max-joltage-12 input)
+  (reduce +)))