day 7

.gitignore

@@ -1,2 +1,5 @@
 *.in
 .metals/
+
+# binaries
+day??

day07.scm

@@ -0,0 +1,41 @@
+(import (chicken string))
+(import (chicken format))
+(import (chicken io))
+(import (chicken sort))
+(import (only traversal enumerate))
+(import srfi-1)
+(import srfi-14)
+(import srfi-60)
+(import srfi-141)
+
+(define numbers (map string->number (string-split (read-line) ",")))
+
+; PART 1
+(define sorted (sort numbers <))
+(define median (list-ref sorted (floor/ (length numbers) 2)))
+
+(define (part1)
+  (foldl
+   (lambda (x y) (+ x (abs (- y median))))
+   0
+   numbers))
+
+
+; PART 2
+(define (triangular n) (/ (* n (+ n 1)) 2))
+
+(define (part2- avg)
+  (foldl
+   (lambda (x y) (+ x (triangular (abs (- y avg)))))
+   0
+   numbers))
+
+(define avgCeil (ceiling/ (foldl + 0 numbers) (length numbers)))
+(define avgFloor (floor/ (foldl + 0 numbers) (length numbers)))
+
+(define (part2)
+  (min (part2- avgCeil) (part2- avgFloor)))
+
+
+(format #t "part 1: ~A~%" (part1))
+(format #t "part 2: ~A~%" (part2))