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(ns aoc-2022.day05)
(require '[aoc-2022.utils :refer :all])
(defn split-by-empty-line [rows]
(split-by "" rows))
(defn revv [v] (vec (rseq v)))
(defn parse-stacks [stacks]
(->> stacks
transpose
(keep-indexed #(if (zero? (mod (- %1 1) 4)) %2 nil))
(map #(filter (partial not= \ ) %))
(map #(drop-last %))
(map vec)))
(defn parse-instrs [instrs]
(->> instrs
(map #(split-by \ %))
(map (partial keep-indexed #(if (odd? %1) (apply str %2) nil)))
(map (partial map to-long))
(map vec)
))
(defn prepare [rows]
(let [[stack-rows instr-rows] (split-by-empty-line rows)
stacks (parse-stacks stack-rows)
instrs (parse-instrs instr-rows)]
(list (vec stacks) (vec instrs))))
(defn run-instr1 [[n from to] stacks]
(if (zero? n)
stacks
(let [from-stack (stacks (dec from))
to-stack (stacks (dec to))
val (first from-stack)
new-from-stack (vec (rest from-stack))
new-to-stack (vec (cons val to-stack))
new-stacks' (assoc stacks (dec from) new-from-stack)
new-stacks (assoc new-stacks' (dec to) new-to-stack)]
(run-instr1 [(dec n) from to] new-stacks))))
(defn run-instrs1 [[instr & is] stacks]
(if (seq instr)
(run-instrs1 (vec is) (run-instr1 instr stacks))
stacks))
(defn task1 [rows]
(let [[stacks instrs] (prepare rows)]
(->> (run-instrs1 instrs stacks)
(map first)
(apply str))))
(defn run-instr2 [[n from to] stacks]
(let [from-stack (stacks (dec from))
to-stack (stacks (dec to))
vals (vec (take n from-stack))
new-from-stack (vec (drop n from-stack))
new-to-stack (vec (concat vals to-stack))
new-stacks' (assoc stacks (dec from) new-from-stack)]
(assoc new-stacks' (dec to) new-to-stack)))
(defn run-instrs2 [[instr & is] stacks]
(if (seq instr)
(run-instrs2 (vec is) (run-instr2 instr stacks))
stacks))
(defn task2 [rows]
(let [[stacks instrs] (prepare rows)]
(->> (run-instrs2 instrs stacks)
(map first)
(apply str))))
(run-aoc "day05" task1 task2)
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