Day 1

.gitignore

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+*~
+inputs/

aoc21.lisp

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+;;; Day 1
+
+(defun read-1 (file)
+  (with-open-file (stream file)
+    (loop for line = (read-line stream nil)
+	  while line
+	  collect (parse-integer line))))
+
+(defun solve-1-1 (file)
+  (let ((readings (read-1 file))
+	(inc-acc 0))
+    (labels ((rec (list old)
+	       (if list
+		   (progn
+		     (if (< old (first list))
+			 (incf inc-acc))
+		     (rec (cdr list) (first list))))))
+      (rec (cdr readings) (first readings))
+      inc-acc)))
+
+(defun solve-1-2 (file)
+  (let ((readings (read-1 file))
+	(inc-acc 0))
+    (labels ((rec (list old-sum)
+	       (if (cddr list)
+		   (let ((sum (reduce #'+ (subseq list 0 3))))
+		     (if (< old-sum sum)
+			 (incf inc-acc))
+		     (rec (cdr list) sum)))))
+      (rec (cdr readings) (reduce #'+ (subseq readings 0 3)))
+      inc-acc)))