AoC 2015.2 p1+2

1 files changed, 51 insertions, 0 deletions

diff --git a/i-was-told-there-would-be-no-math/iwttwbnm.scm b/i-was-told-there-would-be-no-math/iwttwbnm.scm
new file mode 100644
index 0000000..1497be0
--- /dev/null
+++ b/i-was-told-there-would-be-no-math/iwttwbnm.scm
@@ -0,0 +1,51 @@
+(define-module (iwttwbnm)
+  #:use-module (srfi srfi-1)
+  #:export (iwttwbnm
+	    calculate-box
+	    calculate-ribbon))
+
+(define (iwttwbnm str)
+  (let ((dimensions
+	 (map (lambda (line)
+		(map string->number (string-split line #\x)))
+	      (string-split
+	       (string-trim-both str char-set:whitespace)
+	       #\newline))))
+    (list (apply
+	   + (map (lambda (x)
+		    (apply calculate-box x))
+		  dimensions))
+	  (apply
+	   + (map (lambda (x)
+		    (apply calculate-ribbon x))
+		  dimensions)))))
+
+(define (calculate-box l w h)
+  "Given a length L, width W, and
+height H, returns the result of applying
+the following formula:
+
+2*l*w + 2*w*h + 2*h*l + min(l*w, w*h, h*l)"
+  (let* ((lw (* l w))
+	 (wh (* w h))
+	 (hl (* h l))
+	 (areas (list lw wh hl)))
+    (+ (apply + (map (lambda (x)
+		       (* 2 x))
+		     areas))
+       (apply min areas))))
+
+(define (calculate-ribbon l w h)
+  "Given a length L, width W, and
+height H, returns the result of applying
+the following formula:
+
+min(2*(l+w), 2(w*h), 2(h*l)) + l*w*h"
+  (let ((lpw (+ l w))
+	(wph (+ w h))
+	(hpl (+ h l)))
+    (+ (apply min (map (lambda (x)
+			 (* 2 x))
+		       (list lpw wph hpl)))
+       (apply * (list l w h)))))
+