3 files changed, 222 insertions(+), 0 deletions(-)

A resources/day18.example.in
A resources/day18.in
A src/aoc2021/day18.clj

@@ 0,0 1,10 @@
+[[[0,[4,5]],[0,0]],[[[4,5],[2,6]],[9,5]]]
+[7,[[[3,7],[4,3]],[[6,3],[8,8]]]]
+[[2,[[0,8],[3,4]]],[[[6,7],1],[7,[1,6]]]]
+[[[[2,4],7],[6,[0,5]]],[[[6,8],[2,8]],[[2,1],[4,5]]]]
+[7,[5,[[3,8],[1,4]]]]
+[[2,[2,2]],[8,[8,1]]]
+[2,9]
+[1,[[[9,3],9],[[9,0],[0,7]]]]
+[[[5,[7,4]],7],1]
+[[[[4,2],2],6],[8,7]]<
\ No newline at end of file

@@ 0,0 1,100 @@
+[[[[4,0],6],[4,4]],[[6,8],0]]
+[[1,[[1,6],0]],[[[8,9],2],[[0,8],[5,5]]]]
+[[3,8],7]
+[[[8,4],[[4,4],4]],[[3,[0,7]],0]]
+[[[[2,0],[4,5]],[7,[2,8]]],5]
+[[9,7],[[[8,6],3],[8,[0,2]]]]
+[[4,9],[2,[[8,4],2]]]
+[9,[[[2,6],[3,2]],[[2,5],[0,0]]]]
+[[[9,[8,4]],[7,[1,2]]],[[4,[5,6]],[[5,9],[7,5]]]]
+[[[0,[7,5]],[[1,8],1]],[[1,[1,9]],9]]
+[[[0,[4,5]],[[1,2],[5,0]]],9]
+[[[[7,7],3],1],[[0,[0,7]],[[7,1],[1,9]]]]
+[[9,2],[3,[8,[6,1]]]]
+[[8,[5,[3,9]]],[1,[3,8]]]
+[[1,[[4,4],[4,2]]],4]
+[[[5,1],[7,[3,5]]],[[9,[8,4]],9]]
+[[5,[0,4]],[[1,[6,5]],9]]
+[[[1,0],[4,1]],[[1,[3,2]],2]]
+[[[0,[5,9]],[9,[7,2]]],[[4,3],[0,7]]]
+[[[[7,9],[0,4]],[[5,6],[0,7]]],[7,[[1,1],[9,5]]]]
+[[[[2,6],7],[[8,5],8]],[1,6]]
+[[1,[5,5]],[[[3,0],[1,1]],[8,3]]]
+[[[[7,4],5],[1,3]],[[6,9],[[3,7],2]]]
+[[6,[9,[0,6]]],1]
+[8,[4,[2,[2,7]]]]
+[[[7,6],[2,8]],[[4,[8,1]],0]]
+[4,9]
+[[[[6,9],[1,7]],[[4,3],[4,3]]],[[[4,4],[3,6]],[7,[7,0]]]]
+[[[7,4],[[9,1],[9,4]]],[6,[[0,4],[4,6]]]]
+[[[[3,0],[4,7]],[[8,2],[3,9]]],[4,[0,[5,6]]]]
+[[[[1,9],[0,4]],2],[8,[4,[0,9]]]]
+[[[[9,6],[3,7]],4],[7,[[0,9],[5,8]]]]
+[[5,[[4,0],[0,4]]],[[0,1],[2,[6,0]]]]
+[[[2,[9,8]],[[7,9],[6,6]]],[[4,[6,4]],[[2,0],[5,0]]]]
+[[[[5,8],8],[[3,1],1]],[[5,7],5]]
+[[8,[5,1]],[[[5,5],8],[4,6]]]
+[7,[[[3,9],3],[8,6]]]
+[[[[8,6],4],8],[[7,[4,0]],[[8,0],4]]]
+[[[[7,0],8],[[7,7],1]],[[0,5],[[8,2],5]]]
+[4,[3,[3,[6,1]]]]
+[[1,[[7,1],[1,2]]],9]
+[[[9,[5,7]],[4,[4,7]]],8]
+[[[3,[7,2]],[[5,8],6]],[2,0]]
+[8,[0,[[7,4],[3,3]]]]
+[[[[3,4],[1,1]],3],[[[5,3],0],[[0,7],[6,9]]]]
+[3,[[9,1],[3,[0,0]]]]
+[[[[8,8],[3,7]],[7,6]],[[[4,7],[9,5]],[5,8]]]
+[[[[9,0],[5,6]],[[7,9],5]],0]
+[[0,3],[[[9,9],[8,9]],[[7,5],0]]]
+[6,[[2,0],3]]
+[[[9,3],[[6,9],[8,2]]],[7,[[1,3],[0,5]]]]
+[[[[9,5],1],5],[[4,2],[8,[9,5]]]]
+[[8,4],[[4,[8,3]],[8,[8,3]]]]
+[[[[8,0],[4,4]],[5,2]],[[[0,6],[4,0]],[5,8]]]
+[[0,4],[3,[[2,3],7]]]
+[[[[6,9],[3,0]],8],[[[4,7],[6,1]],[2,0]]]
+[5,[[9,[5,1]],7]]
+[[[8,0],[[5,0],0]],[[4,[0,7]],[[6,4],0]]]
+[[[1,[0,2]],1],8]
+[[[[4,8],[2,0]],[[0,4],9]],[4,[[9,8],[3,8]]]]
+[[[1,[6,0]],[6,5]],[3,4]]
+[[2,[[4,3],[4,4]]],[[[9,7],8],[5,0]]]
+[[[[1,6],2],[[3,5],0]],[[[4,3],[8,1]],[[5,2],[2,1]]]]
+[[[[4,8],[1,2]],[9,[3,7]]],[1,[4,4]]]
+[[[[2,7],[5,8]],[[2,4],[6,8]]],[9,8]]
+[[[1,5],[7,0]],[[8,7],4]]
+[[[5,3],[[0,3],[6,2]]],[[8,[7,4]],[5,6]]]
+[[[[1,4],1],[8,[2,0]]],[[[0,0],[7,9]],[[1,8],3]]]
+[[[[0,0],[4,3]],2],3]
+[[[8,[8,9]],[1,[6,1]]],[[6,[5,5]],[5,[9,5]]]]
+[[[6,[4,2]],[[1,4],[5,6]]],[0,[[5,9],[2,7]]]]
+[3,[[[2,5],2],8]]
+[[2,[6,[1,6]]],[0,[4,[9,2]]]]
+[[[[7,6],[5,9]],[6,[6,0]]],[2,[3,[1,4]]]]
+[[[[1,7],[7,4]],[[6,0],[5,3]]],[2,[[5,2],0]]]
+[[[7,[6,1]],[[1,7],[7,2]]],[5,6]]
+[[3,2],[6,[9,7]]]
+[[[7,[7,5]],[[0,9],5]],[[4,[5,6]],[[8,6],[1,8]]]]
+[[[1,[1,6]],7],2]
+[[[7,[6,2]],3],[[[5,5],6],9]]
+[[[1,[9,8]],[0,5]],[[[2,4],5],[[5,6],7]]]
+[[[9,[1,1]],[7,0]],[[5,8],2]]
+[[[[8,5],[3,0]],[1,[2,6]]],[[[4,3],[3,2]],0]]
+[[[[0,5],7],[7,1]],[4,[[3,4],[9,5]]]]
+[[[7,6],[5,1]],[9,3]]
+[[[[5,4],6],[2,[0,6]]],[[[6,0],[9,5]],[[8,6],[3,4]]]]
+[[0,[6,[9,6]]],[[[1,2],[9,6]],[0,[6,2]]]]
+[[[[7,7],6],7],[[8,[0,5]],[0,2]]]
+[[[[6,7],[0,7]],[6,[5,0]]],[6,7]]
+[[7,[1,8]],[[2,3],[[7,0],3]]]
+[[8,[5,7]],[[3,[6,5]],4]]
+[[9,9],[[[9,9],9],[2,3]]]
+[[[[0,6],[1,4]],5],[1,3]]
+[[[9,[8,8]],[[9,9],7]],[2,[[7,1],6]]]
+[[[1,8],[1,3]],[[[8,1],8],[[4,2],1]]]
+[[4,2],[[[0,7],5],7]]
+[[[6,[3,6]],[[0,2],[5,6]]],[[0,1],[[0,9],2]]]
+[[[[4,5],[1,4]],1],[[[4,7],[2,3]],6]]
+[[[2,2],[0,6]],[[6,[6,4]],1]]
+[[[5,[7,7]],[[7,0],1]],2]<
\ No newline at end of file

@@ 0,0 1,112 @@
+; --- Day 18: Snailfish ---
+; https://adventofcode.com/2021/day/18
+
+(ns aoc2021.day18
+  (:require [clojure.java.io :as io]
+            [clojure.string :as str]
+            [clojure.pprint :refer [pprint]]
+            [clojure.edn :as edn]
+            [clojure.zip :as zip]))
+
+(def input-file (-> "day18.example.in" io/resource io/file))
+; (def input-file (-> "day18.in" io/resource io/file))
+
+(defn get-input []
+  (map (fn [line] (edn/read-string (str/replace line #"," " ")))
+    (-> input-file slurp str/split-lines)))
+
+(defn depth
+  ([loc] (depth loc 0))
+  ([loc depth]
+   (if (nil? (zip/up loc))
+     depth
+     (recur (zip/up loc) (inc depth)))))
+
+(defn explodable? [loc]
+  (and (vector? (zip/node loc))
+       (= (depth loc) 4)))
+
+(defn splittable? [loc]
+  (let [node (zip/node loc)]
+    (and (integer? node)
+         (>= node 10))))
+
+(defn number? [loc]
+  (integer? (zip/node loc)))
+
+(defn add-left [start-loc n]
+  (loop [loc start-loc]
+    (let [loc (zip/prev loc)]
+      (cond
+        (nil? loc) start-loc
+        (number? loc) (zip/edit loc + n)
+        true (recur loc)))))
+
+(defn add-right [start-loc n]
+  (loop [loc start-loc]
+    (let [loc (zip/next loc)]
+      (cond
+        (zip/end? loc) start-loc
+        (number? loc) (zip/edit loc + n)
+        true (recur loc)))))
+
+(defn move-right [loc]
+  (let [loc (zip/next loc)]
+    (if (number? loc)
+      loc
+      (move-right loc))))
+
+; if add-left finds a left element, it will increment it by left value and
+; return the zipper at that position. if there is no left element, it will
+; return the zipper at starting position. in the former case we need to move
+; one step right before running add-right. not very elegant.
+(defn maybe-move-right [loc prev-loc]
+  (if (= loc prev-loc)
+    loc
+    (move-right loc)))
+
+(defn rewind [loc]
+  (zip/vector-zip (zip/root loc)))
+
+(defn explode [loc]
+  (println "explode" (zip/node loc))
+  (let [[left right] (zip/node loc)
+        loc (zip/replace loc 0)]
+    (-> loc
+        (add-left left)
+        (maybe-move-right loc)
+        (add-right right))))
+
+(defn split [loc]
+  (println "split" (zip/node loc))
+  (let [n (zip/node loc)
+        l (quot n 2)
+        r (+ l (rem n 2))]
+    (zip/replace loc [l r])))
+
+(defn step [loc]
+  (if (zip/end? loc)
+    nil
+    (let [loc (zip/next loc)]
+      (cond
+        (explodable? loc) (rewind (explode loc))
+        (splittable? loc) (rewind (split loc))
+        true (recur loc)))))
+
+(defn reduce' [numbers]
+  (let [loc (zip/vector-zip numbers)]
+    (loop [loc loc]
+      (println (zip/root loc))
+      (let [next (step loc)]
+        (if (nil? next)
+          (zip/root loc)
+          (recur next))))))
+
+(defn add [left right]
+  (println "add" [left right])
+  (reduce' [left right]))
+
+(defn main []
+  (let [numbers (get-input)]
+    (println "\nactual:  " (reduce add (take 2 numbers)))
+    (println "expected: [[[[4 0] [5 4]] [[7 7] [6 0]]] [[8 [7 7]] [[7 9] [5 0]]]]")))