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(defun next-house (house i)
  (destructuring-bind (x y) house
    (case i
      (#\> (list (+ x 1) y))
      (#\< (list (- x 1) y))
      (#\^ (list x (+ y 1)))
      (t (list x (- y 1))))))

(defun count-unique-deliveries-by-santa (file)
  (with-open-file (stream file)

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(defun box-dimensions (box-string)
  "Given the dimensions of a box as a string in the form 'XxYxZ', return a
   sequence containing the dimensions as integers X, Y and Z, sorted in
   ascending order."
  (sort (mapcar #'parse-integer
                (str:split "x" box-string))
        #'<))

(defun paper-for-box (box)
  "Given the dimensions of BOX as integers sorted in ascending order, return

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(defparameter *instruction->move*
              '((#\( . 1+)
                (#\) . 1-))
  "Map instructions to floor movements.")

(defun all-floors (instructions)
  "Return a sequence of all floors passed through when starting at floor 0 and
   following the list of INSTRUCTIONS."
  (reverse (reduce #'(lambda (acc i)
                       (cons (funcall (cdr (assoc i *instruction->move*))

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(ns blocks-world.core)

(def ^:private database
  "The blocks database."
  [[:b1 :shape :brick]
   [:b1 :color :green]
   [:b1 :size :small]
   [:b1 :supported-by :b2]
   [:b1 :supported-by :b3]
   [:b2 :shape :brick]

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(ns robbie.core)

(def rooms
  "Robbie's world."
  {:living-room {:north :front-stairs
                 :south :dining-room
                 :east :kitchen}
   :upstairs-bedroom {:west :library
                      :south :front-stairs}
   :dining-room {:north :living-room

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(ns compare-descriptions.core
  (:require [clojure.set :only intersection]))

(defn- right-side
  "Given a list containing the descriptions of two objects separated by the
   keyword :-vs-, return the description of the object to the right of the
   separator."
  [descriptions]
  (rest (drop-while #(not= % :-vs-)
          descriptions)))

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(ns day-1.core)

(def input (slurp "input.txt"))

(def up \()

(defn where-is-santa
  "What floor will Santa finish on after following INSTRUCTIONS?"
  [instructions]
  (reduce #(+ %1

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(ns day-2.core)

(defn box-dimensions
  "Given the dimensions of a box in the form \"XxYxZ\", return a sorted
   sequence of X, Y and Z."
  [box]
  (sort (map parse-long
             (re-seq #"[0-9]+" box))))

(def boxes

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(ns day-2.core
  (:require [clojure.string :as str]))

(def rounds
  "Return a sequence of all the rounds of the game."
  (str/split (slurp "input.txt")
             #"\n"))

(defn plan-a
  [round]

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(ns day-1.core
  (:require [clojure.string :as string]))

(defn- calories-per-elf
  "The amount of calories each elf is carrying, greatest value first."
  [input-file-name]
  (sort >
        (map #(reduce +
                      (map parse-long
                           (re-seq #"[0-9]+" %)))