X-Git-Url: http://git.jkinsey.net/?p=adventofcode2019.git;a=blobdiff_plain;f=src%2Fadventofcode2019%2Fday12.clj;fp=src%2Fadventofcode2019%2Fday12.clj;h=28ad0b2783d56ae33132fd918c0077ff65c86f13;hp=0000000000000000000000000000000000000000;hb=2441c6e83817ce81f250f943ea252f866957bee8;hpb=9205379113b838bcad0f87d9dfa770fc7c3d0b83

diff --git a/src/adventofcode2019/day12.clj b/src/adventofcode2019/day12.clj
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+++ b/src/adventofcode2019/day12.clj
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+(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]]])
+
+; <x=1, y=2, z=3> -> [[1 2 3] [0 0 0]]
+(defn parse-coords [coords]
+  [(mapv parse-int (str/split (str/replace coords #"[<>xyz=,]" "") #" "))
+   [0 0 0]])
+
+(defn gravity [[pos1 vel1] [pos2 vel2]]
+  (let [adjust-velocity (fn [a b]
+                          (cond
+                            (< a b) [inc dec]
+                            (= a b) [identity identity]
+                            (> a b) [dec inc]))
+        velocity-diffs (map adjust-velocity pos1 pos2)
+        apply-diffs (fn [acc vel] (mapv #(%1 %2) (map acc velocity-diffs) vel))]
+    [(apply-diffs first vel1)
+     (apply-diffs second vel2)]))
+
+(defn velocity [[pos vel]]
+  [(mapv + pos vel) vel])
+
+(defn total-energy [[pos vel]]
+  (let [abs+ (fn [& args] (apply + (map #(Math/abs %) args)))
+        potential (apply abs+ pos)
+        kinetic (apply abs+ vel)]
+    (* potential kinetic)))
+
+(defn step-simulation [bodies]
+  (let [indices (range (count bodies))
+        all-pairs (combo/combinations indices 2)
+        apply-gravity (fn [bodies [i j]]
+                        (let [[nv1 nv2] (gravity (bodies i) (bodies j))]
+                          (-> bodies
+                              (assoc-in [i 1] nv1)
+                              (assoc-in [j 1] nv2))))]
+    (mapv velocity (reduce apply-gravity bodies all-pairs))))
+
+(defn day12 []
+  (let [input (map parse-coords (get-list-from-file (input-file)))
+        simulate (iterate step-simulation input)] 
+    (part1 (reduce + (map total-energy (nth simulate 1000))))
+    #_(part2)))