day 7

src/day7.clj

@@ -0,0 +1,65 @@
+(ns day7
+  (:require [clojure.string :as string]
+            [helpers :refer [get-input]]))
+
+(def example
+".......S.......
+...............
+.......^.......
+...............
+......^.^......
+...............
+.....^.^.^.....
+...............
+....^.^...^....
+...............
+...^.^...^.^...
+...............
+..^...^.....^..
+...............
+.^.^.^.^.^...^.
+...............")
+
+
+;(def input (mapv (partial apply vector) (string/split-lines example)))
+(def input (mapv (partial apply vector) (string/split-lines (get-input 7))))
+
+(def line-len (count input))
+(def column-len (count (first input)))
+
+(def start [0 (.indexOf (apply str (first input)) "S")])
+
+(def split (atom 0))
+
+(defn prop [[l c]]
+  (if (= \^ (get-in input [l c]))
+    (do (swap! split inc)
+        [[l (dec c)] [l (inc c)]])
+    [[l c]]))
+
+(defn propagate [beams]
+  (->>
+   beams
+   (map (fn [[l c]] [(inc l) c]))
+   (mapcat prop)))
+
+(loop [beams [start]]
+  (if (< (-> beams first first) column-len)
+    (recur (set (propagate beams)))
+    (println "Beam split" @split "times")))
+
+(def memo (atom {}))
+
+(def timelines
+  (memoize
+   (fn [[l c]]
+     (cond
+       (or (neg? l) (neg? c) (>= c column-len) (>= l line-len))
+       1
+       (= \^ (get-in input [l c]))
+       (+ (timelines [(inc l) (inc c)])
+          (timelines [(inc l) (dec c)]))
+       :else
+       (timelines [(inc l) c])))))
+
+(println "Timelines:" (timelines start))