Day 2

aoc21.lisp

@@ -29,3 +29,41 @@
 		     (rec (cdr list) sum)))))
       (rec (cdr readings) (reduce #'+ (subseq readings 0 3)))
       inc-acc)))
+
+;;; Day 2
+
+(defun setup-solution-2 (stage)
+  (let ((position (vector 0 0))
+	(aim 0))
+    (defun forward (n)
+      (incf (elt position 0) n)
+      (if (= stage 2) (incf (elt position 1) (* n aim))))
+    (defun up (n)
+      (if (= stage 1)
+	  (decf (elt position 1) n)
+	  (decf aim n)))
+    (defun down (n)
+      (if (= stage 1)
+	  (incf (elt position 1) n)
+	  (incf aim n)))
+    (defun zero ()
+      (setf position (vector 0 0) aim 0))
+    (defun result ()
+      position)))
+
+(defun read-2-1 (file)
+  (with-open-file (stream file)
+    (loop for line = (read-line stream nil)
+	  while line
+	  collect (multiple-value-bind (symbol length) (read-from-string line)
+		    (list symbol (parse-integer (subseq line length)))))))
+
+(defun solve-2-1 (data)
+  (setup-solution-2 1)
+  (eval (cons 'progn data))
+  (reduce #'* (result)))
+
+(defun solve-2-2 (data)
+  (setup-solution-2 2)
+  (eval (cons 'progn data))
+  (reduce #'* (result)))