1 files changed, 27 insertions, 0 deletions
diff --git a/year2021/day2/part2.clj b/year2021/day2/part2.clj
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+++ b/year2021/day2/part2.clj
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+; Day 2, part 2
+; Read a list of instructions from stdin:
+;   "down X" increases aim number by X,
+;   "up X" decreases aim by X,
+;   "forward X" increases xpos by X and depth by (aim * X).
+; Print (xpos * depth) after end of data.
+;
+
+(require '[clojure.string :as str])
+
+(println
+  (apply *
+    (map
+      (reduce
+        #(case (first %2)
+           "forward" (-> %1 (update :xpos + (second %2))
+                            (update :depth + (* (%1 :aim) (second %2))))
+           "up"      (update %1 :aim - (second %2))
+           "down"    (update %1 :aim + (second %2)))
+        {:xpos 0 :depth 0 :aim 0}
+        (->> (slurp "./in")
+             str/split-lines
+             (map #(str/split % #" "))
+             (map #(update % 1 read-string))))
+      [:xpos :depth]
+      )))
+