From 7c0dd5d118d60fb7ef1094f6664237f79a54240e Mon Sep 17 00:00:00 2001
From: Leah Neukirchen <leah@vuxu.org>
Date: Mon, 20 Dec 2021 17:42:32 +0100
Subject: day19

---
 day19.clj | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 day19.clj

(limited to 'day19.clj')

diff --git a/day19.clj b/day19.clj
new file mode 100644
index 0000000..9465025
--- /dev/null
+++ b/day19.clj
@@ -0,0 +1,94 @@
+(ns org.vuxu.aoc2021.day19
+  (:require [clojure.string :as str]
+            [clojure.set :as set]))
+
+(def data
+  (for [scanner (str/split (slurp "day19") #"\n\n")]
+    (->> (str/split-lines scanner)
+         (drop 1)
+         (map #(str/split % #","))
+         (mapv (partial mapv parse-long)))))
+
+(def axes [[0 1 0] [0 -1 0] [1 0 0] [-1 0 0] [0 0 1] [0 0 -1]])
+
+(defn transform [[x y z] up rot]
+  (let [[rx ry rz] (case up
+                     [ 0  1  0] [x y z]
+                     [ 0 -1  0] [x (- y) (- z)]
+                     [ 1  0  0] [y x (- z)]
+                     [-1  0  0] [y (- x) z]
+                     [ 0  0  1] [y z x]
+                     [ 0  0 -1] [y (- z) (- x)])]
+    (case rot
+      0 [rx ry rz]
+      1 [rz ry (- rx)]
+      2 [(- rx) ry (- rz)]
+      3 [(- rz) ry rx])))
+
+(defn translate [p v]
+  (mapv + p v))
+
+(defn diff [v1 v2]
+  (mapv - v1 v2))
+
+(defn align [beacons1 beacons2]
+  (first
+   (for [axis axes
+         rotation (range 4)
+         :let [rotated-beacons2 (map #(transform % axis rotation) beacons2)]
+         b1 beacons1
+         matching-b1-in-b2 rotated-beacons2
+         :let [delta (diff b1 matching-b1-in-b2)
+               transformed-beacons2 (set (map #(translate % delta) rotated-beacons2))
+               intersection (set/intersection transformed-beacons2 beacons1)]
+         :when (>= (count intersection) 12)]
+     [transformed-beacons2 delta axis rotation])))
+
+(defn reduc [scans scanners]
+  (let [[to-remove scans scanners]
+        (loop [to-remove #{}
+               scans scans
+               scanners scanners
+               i 0
+               j 1]
+          (prn [i j])
+          (if (>= i (dec (count scans)))
+            [to-remove scans scanners]
+            (if (>= j (count scans))
+              (recur to-remove scans scanners (inc i) (+ i 2))
+              (if (to-remove j)
+                (recur to-remove scans scanners i (inc j))
+                
+                (if-let [[agt trs up rot] (align (scans i) (scans j))]
+                  (recur (conj to-remove j)
+                         (update scans i set/union agt)
+                         (update scanners i set/union
+                                 (set (map #(translate trs (transform % up rot)) (scanners j))))
+                         i
+                         (inc j))
+                  (recur to-remove scans scanners i (inc j)))))))]
+    [(vec (keep-indexed #(when (not (to-remove %1)) %2) scans))
+     (vec (keep-indexed #(when (not (to-remove %1)) %2) scanners))]))
+
+;; very slow :/
+(def reducd
+  (loop [[scans scanners]
+         [(mapv set data) (mapv (constantly #{[0 0 0]}) data)]]
+    (if (> (count scans) 1)
+      (recur (reduc scans scanners))
+      [(first scans)
+       (first scanners)])))
+
+(def part1
+  (count (first reducd)))
+;; => 445
+
+(defn manhattan [a b]
+  (apply + (map #(Math/abs %) (diff a b))))
+
+(def part2
+  (apply max
+         (for [b1 (second reducd)
+               b2 (second reducd)]
+           (manhattan b1 b2))))
+;; => 13225
-- 
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