Add solution for day 4

day04/day04.lisp

@@ -0,0 +1,28 @@
+(ql:quickload :cl-ppcre)
+
+(defun string-to-sequence (range)
+  (let* ((range (cl-ppcre:split "-" range))
+	 (lower (parse-integer (first range)))
+	 (upper (parse-integer (second range))))
+    (loop :for x :from lower :to upper :collect x)))
+
+(defun parse-input (input)
+  (cl-ppcre:split "\\n" (uiop:read-file-string input)))
+
+(defun containp (pair)
+  (let ((left (string-to-sequence (first (ppcre:split "," pair))))
+	(right (string-to-sequence (second (ppcre:split "," pair)))))
+    (cond ((search left right) t)
+	  ((search right left) t)
+	  (t NIL))))
+
+(defun part-one (input)
+  (count 't (mapcar #'containp (parse-input input))))
+
+(defun overlapp (pair)
+  (let ((left (string-to-sequence (first (ppcre:split "," pair))))
+	(right (string-to-sequence (second (ppcre:split "," pair)))))
+    (if (intersection left right) t)))
+
+(defun part-two (input)
+  (count 't (mapcar #'overlapp (parse-input input))))