X-Git-Url: http://git.jkinsey.net/?p=adventofcode2019.git;a=blobdiff_plain;f=src%2Fadventofcode2019%2Fday12.clj;fp=src%2Fadventofcode2019%2Fday12.clj;h=d10e74b514cf7d427c7571a086cfc8f5d56b7ee0;hp=7326e425a72c8d73c9759ee06ef7c8ef480e0d8e;hb=0449019578dbfc4c0b280578cb9e48d5bb1e1079;hpb=fa02619ed39b05a9d8bb83e73aac4779dd38cac5

diff --git a/src/adventofcode2019/day12.clj b/src/adventofcode2019/day12.clj
index 7326e42..d10e74b 100644
--- a/src/adventofcode2019/day12.clj
+++ b/src/adventofcode2019/day12.clj
@@ -1,10 +1,10 @@
 (ns adventofcode2019.day12
-    [:require [adventofcode2019.lib :refer :all]
-              [adventofcode2019.intcode :as i]
-              [clojure.string :as str]
-              [clojure.core.match :refer [match]]
-              [clojure.math.combinatorics :as combo]
-              [clojure.pprint :refer [pprint]]])
+  [:require [adventofcode2019.lib :refer :all]
+   [adventofcode2019.intcode :as i]
+   [clojure.string :as str]
+   [clojure.core.match :refer [match]]
+   [clojure.math.combinatorics :as combo]
+   [clojure.pprint :refer [pprint]]])
 
 ; <x=1, y=2, z=3> -> [[1 2 3] [0 0 0]]
 (defn parse-coords [coords]
@@ -41,8 +41,16 @@
                               (assoc-in [j 1] nv2))))]
     (mapv velocity (reduce apply-gravity bodies all-pairs))))
 
+(defn find-cycle [states]
+  (let [detect-dup (fn [[ct prev] state]
+                     (if (= (flatten prev)
+                            (map - (flatten state)))
+                       (reduced (inc ct))
+                       [(inc ct) state]))]
+    (* 2 (reduce detect-dup [0 []] states))))
+
 (defn day12 []
   (let [input (mapv parse-coords (get-list-from-file (input-file)))
-        simulate (iterate step-simulation input)] 
+        simulate (iterate step-simulation input)]
     (part1 (reduce + (map total-energy (nth simulate 1000))))
-    #_(part2)))
+    (part2 (find-cycle simulate))))