path: root/day01.lisp

(defun input-lines (f)
  (with-open-file (s f)
    (loop for line = (read-line s nil 'eof)
          until (eq line 'eof)
          collect line)))

(defun collect-line-digits (line)
  (loop for char across line
        if (digit-char-p char)
          collect (digit-char-p char)))

(defun calibration-value (numbers)
  (let ((fst (first numbers))
        (lst (car (last numbers))))
    (+ (* 10 fst) lst)))

(defun calibration-values (lnumbers)
  (mapcar #'calibration-value lnumbers))

(defun solve1 (f)
  (let ((lnumbers (mapcar #'collect-line-digits (input-lines f))))
    (reduce #'+ (calibration-values lnumbers))))

(defun string-compare (s1 s2 begin)
  (let ((l1 (array-total-size s1))
        (l2 (- (array-total-size s2) begin)))
    (if (>= l2 l1)
        (equalp s1 (subseq s2 begin (+ begin l1))))))

(defun string-digit-text-p (s begin)
  (cond ((string-compare "zero"  s begin) 0)
        ((string-compare "one"   s begin) 1)
        ((string-compare "two"   s begin) 2)
        ((string-compare "three" s begin) 3)
        ((string-compare "four"  s begin) 4)
        ((string-compare "five"  s begin) 5)
        ((string-compare "six"   s begin) 6)
        ((string-compare "seven" s begin) 7)
        ((string-compare "eight" s begin) 8)
        ((string-compare "nine"  s begin) 9)))

(defun string-digit-p (s begin)
  (let ((digit (digit-char-p (aref s begin))))
    (if digit
        digit
        (string-digit-text-p s begin))))

(defun collect-line-digits2 (line)
  (loop with l = (array-total-size line)
        for i from 0 to (- l 1)
        as d = (string-digit-p line i)
        when d
          collect d))

(defun solve2 (f)
  (let ((lnumbers (mapcar #'collect-line-digits2 (input-lines f))))
    (reduce #'+ (calibration-values lnumbers))))

(print (solve1 "data/01/example1.txt"))
(print (solve1 "data/01/input.txt"))
(print (solve2 "data/01/example2.txt"))
(print (solve2 "data/01/input.txt"))