aoc20/aoc20.lisp

;;;; AoC 2020

;;; Day 1

(defun read-1 (file)
  (with-open-file (stream file)
    (loop for line = (read-line stream nil)
	  while line
	  collect (parse-integer line))))

(defvar *input-1-0* nil)
(setf *input-1-0* (read-1 "inputs/1-0"))
(defvar *input-1-1* nil)
(setf *input-1-1* (read-1 "inputs/1-1.txt"))

(defun solve-1-1 (data target)
  (let ((deficits (map 'list (lambda (n) (- target n)) data)))
    (reduce #'* (intersection data deficits))))

(defun make-deficits (list difference)
  (map 'list (lambda (n) (- difference n)) list))


(defun solve-1-2 (data target)
  (let ((first-deficits (make-deficits data target)))
    (reduce #'*
	    (remove-duplicates
	     (mapcan (lambda (n)
		       (intersection (make-deficits data n) data))
		     first-deficits)))))

(defun solve-1 (data target)
  (time (progn
	  (print (solve-1-1 data target))
	  (print (solve-1-2 data target)))))

;;; Day 2

(defstruct password
  (pchar)
  (prange)
  (word))

(defun read-2 (file)
  (with-open-file (stream file)
    (loop for line = (read-line stream nil)
	  while line
	  collect (let* ((pwlist (split-sequence:split-sequence #\space line))
			 (range (multiple-value-bind (n index)
				    (parse-integer (first pwlist) :junk-allowed t)
				  (list n (parse-integer (first pwlist) :start (1+ index))))))
		    (make-password
		     :pchar (char (second pwlist) 0)
		     :prange range
		     :word (third pwlist))))))

(defun %solve-2-1 (pw)
  (let ((n (count (password-pchar pw) (password-word pw))))
    (and (not (> (first (password-prange pw)) n))
	 (not (< (second (password-prange pw)) n)))))

(defun %solve-2-2 (pw)
  (let ((valid 0))
    (loop for index in (password-prange pw)
	  do (if (eq (password-pchar pw) (elt (password-word pw) (1- index)))
		 (incf valid)))
    (= valid 1)))

(defun %solve-2 (data test)
  (let ((pn 0))
    (loop for p in data
	  do (if (funcall test p)
		 (incf pn)))
    pn))

(defun solve-2 (file)
  (let ((data (read-2 file)))
    (time (progn (print (%solve-2 data #'%solve-2-1))
		 (print (%solve-2 data #'%solve-2-2))))))

;;; Day 3

(defun read-3 (file)
  (with-open-file (stream file)
    (let ((temp-map (loop for line = (read-line stream nil)
			  while line
			  collect line)))
      (make-array (list (length temp-map) (length (first temp-map)))
		  :initial-contents temp-map
		  :element-type 'character))))

(defun step-slope (position direction map)
  (let* ((temp-position (map 'list #'+ direction position))
	 (overflow (map 'list #'> temp-position (array-dimensions map))))
    (cond ((first overflow) :bottom)
	  ((second overflow)
	   (progn (decf (second temp-position) (second (array-dimensions map)))
		  temp-position))
	  (t temp-position))))

(defun solve-3-1 (direction map)
  (let ((tree-count 0))
    (labels ((rec (position)
	       (let ((zero-pos (map 'list #'1- position))
		     (new-pos (step-slope position direction map)))
		 (if (char= (aref map (first zero-pos) (second zero-pos))
			    #\#)
		     (incf tree-count))
		 (unless (eq new-pos :bottom)
		   (rec new-pos)))))
      (rec '(1 1))
      tree-count)))

;; (height width)

(defun solve-3-2 (slopes map)
  (reduce #'* (loop for slope in slopes
		    collecting (solve-3-1 slope map))))

(defun solve-3 (map)
  (time (let ((data (read-3 map)))
	  (print (solve-3-1 '(1 3) data))
	  (print (solve-3-2 '((1 1) (1 3) (1 5) (1 7) (2 1)) data)))))

;;; Day 4

(defvar *passport-fields* (list "byr" "iyr" "eyr" "hgt" "hcl" "ecl" "pid" "cid"))
(defvar *passport-rules-broken* (list nil nil nil nil nil nil nil (lambda (n) (declare (ignore n)) t)))
(defvar *passport-rules* nil)
(setf *passport-rules*
      (list (lambda (n) (and n (let ((nn (ignore-errors (parse-integer n))))
				 (and nn (>= nn 1920) (<= nn 2002)))))
	    (lambda (n) (and n (let ((nn (ignore-errors (parse-integer n))))
				 (and nn (>= nn 2010) (<= nn 2020)))))
	    (lambda (n) (and n (let ((nn (ignore-errors (parse-integer n))))
				 (and nn (>= nn 2020) (<= nn 2030)))))
	    (lambda (h) (and h (multiple-value-bind (n offset) (parse-integer h :junk-allowed t)
				 (let ((unit (subseq h offset)))
				   (cond ((string= unit "cm")
					  (and (>= n 150) (<= n 193)))
					 ((string= unit "in")
					  (and (>= n 59) (<= n 76))))))))
	    (lambda (c) (and c
			     (= (length c) 7)
			     (char= (elt c 0) #\#)
			     (parse-integer (subseq c 1) :radix 16)))
	    (lambda (c) (and c (member c '("amb" "blu" "brn" "gry" "grn" "hzl" "oth") :test #'equal)))
	    (lambda (pid)  (and pid
				(= 9
				   (length pid)
				   (length (remove-if (lambda (n) (not (digit-char-p n))) pid)))))
	    (lambda (cid) (declare (ignore cid)) t)))

(defun read-passport (stream)
  (let ((passport-list
	  (apply #'concatenate 'list 
		 (loop for line = (read-line stream nil)
		       while (and line (not (string= line "")))
		       collect (split-sequence:split-sequence #\space line))))
	(current-passport (make-hash-table :test 'equal)))
    (loop for key in passport-list
	  do (setf (gethash (subseq key 0 3) current-passport)
		   (subseq key 4)))
    current-passport))

(defun read-4 (file)
  (with-open-file (stream file)
    (loop while (peek-char nil stream nil)
	  collect (read-passport stream))))

(defun %solve-4 (data tests)
  (let ((valid-count 0))
    (loop for passport in data
	  do (unless (member 'nil
			      (map 'list (lambda (field test)
					   (if test
					       (funcall test (gethash field passport))
					       (gethash field passport)))
				   *passport-fields* tests))
	       (incf valid-count)))
    valid-count))

(defun solve-4 (file)
  (let ((data (read-4 file)))
    (time (progn (print (%solve-4 data *passport-rules-broken*))
		 (print (%solve-4 data *passport-rules*))))))

(defun binarize (string bits)
  (parse-integer (substitute
		  #\1 (elt bits 1)
		  (substitute
		   #\0 (elt bits 0) string))
		 :radix 2))

;;; Day 5

(defun read-5 (file)
  (with-open-file (stream file)
    (loop for line = (read-line stream nil)
	  while line
	  collect (map 'list #'binarize (list (subseq line 0 7) (subseq line 7)) '("FB" "LR")))))

(defun boarding-ids (data)
  (map 'list (lambda (seat) (+ (* 8 (first seat)) (second seat))) data))

(defun solve-5-1 (data)
  (first (sort (boarding-ids data) #'>)))

(defvar p1-answer)

(defun report-significant-difference (x y)
  (if (not (= (- x y) 1))
      (setf p1-answer (1- x)))
  y)

(defun solve-5-2 (data)
  (reduce #'report-significant-difference (sort (boarding-ids data) #'>)))

(defun solve-5 (file)
  (declare (special p1-answer))  (let ((data (read-5 file))
	(p1-answer nil))
    (time (progn (print (solve-5-1 (copy-seq data)))
		 (solve-5-2 data)
		 (print p1-answer)))))

;;; Day 6

(defun read-forms (stream)
  (loop for line = (read-line stream nil)
	while (and line (not (string= line "")))
	collect line))

(defun read-6 (file)
  (with-open-file (stream file)
    (loop while (peek-char nil stream nil)
	  collect (read-forms stream))))

(defun solve-6-1 (data)
  (reduce (lambda (x y) (+  (if (consp x) (length x) x) (length y)))
	  (map 'list (lambda (form) (remove-duplicates (apply #'concatenate 'list form))) data)))

(defun solve-6-2 (data)
  (length (mapcan (lambda (entry)
		    (reduce #'intersection (map 'list (lambda (l) (coerce l 'list)) entry)))
		  data)))

(defun solve-6 (file)
  (let ((data (read-6 file)))
    (time (progn (print (solve-6-1 data))
		 (print (solve-6-2 data))))))