advent-14.clj

(ns advent.a14
  (:require [clojure.string :as str]))

(def rules "Rudolph can fly 22 km/s for 8 seconds, but then must rest for 165 seconds.
Cupid can fly 8 km/s for 17 seconds, but then must rest for 114 seconds.
Prancer can fly 18 km/s for 6 seconds, but then must rest for 103 seconds.
Donner can fly 25 km/s for 6 seconds, but then must rest for 145 seconds.
Dasher can fly 11 km/s for 12 seconds, but then must rest for 125 seconds.
Comet can fly 21 km/s for 6 seconds, but then must rest for 121 seconds.
Blitzen can fly 18 km/s for 3 seconds, but then must rest for 50 seconds.
Vixen can fly 20 km/s for 4 seconds, but then must rest for 75 seconds.
Dancer can fly 7 km/s for 20 seconds, but then must rest for 119 seconds.")

(defn parse-int [s]
  (Integer/parseInt s))

(defn parse [rule]
  (let [[_ vel time rest] (re-find #".*?(\d+) km/s for (\d+) seconds.*?(\d+) seconds." rule)]
    (map parse-int [vel time rest])))

(defn vel-at-second [[vel time rest]]
  (cycle (concat (repeat time vel) (repeat rest 0))))

(defn distance-at [time vs]
  (reduce + (take time (vel-at-second vs))))o

(defn rolling-sum [is]
  (reduce (fn [r i] (conj r (+ (or (last r) 0) i))) [] is))

(defn transpose [vss]
  (for [i (range (count (first vss)))]
    (for [vs vss]
      (nth vs i))))

(defn score-race [vss]
  (transpose
   (for [vs (transpose vss)]
     (let [fstst (apply max vs)]
       (for [v vs]
         (if (== v fstst) 1 0))))))

(let [time 2503]
  (->> (str/split-lines rules)
       (map parse)
       (map vel-at-second)
       (map (partial take time))
       (map rolling-sum)
       score-race
       (map #(reduce + %))
       (apply max)))