1 files changed, 29 insertions, 0 deletions
diff --git a/05/lib.scm b/05/lib.scm
new file mode 100644
index 0000000..9a9951b
--- /dev/null
+++ b/05/lib.scm
@@ -0,0 +1,29 @@
+(library (lib)
+  (export solve-part1 solve-part2)
+  (import (chezscheme))
+
+  ; Follow the jump instructions until we end up outside,
+  ; updating every offset we touch according to `proc'
+  (define (solve-puzzle proc lines)
+    (define code (list->vector (map string->number lines)))
+    (let loop ((i 0) (count 0))
+      (if (or (< i 0) (>= i (vector-length code)))
+          count
+          (let ((offset (vector-ref code i)))
+            (vector-set! code i (proc offset))
+            (loop (+ i offset) (+ count 1))))))
+
+  (define (solve-part1 lines)
+    (solve-puzzle
+      (lambda (offset) (+ offset 1))
+      lines))
+
+  (define (solve-part2 lines)
+    (solve-puzzle
+      (lambda (offset)
+        (if (>= offset 3)
+          (- offset 1)
+          (+ offset 1)))
+      lines))
+
+)