From 10fd78b85ae5ba3b2cf6ab25c2795b95ab468084 Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Thu, 14 Dec 2017 01:12:08 -0500
Subject: [PATCH] d14 s1

---
 2017/d14/main.rkt  | 40 ++++++++++++++++++++++++++++++++++++++++
 2017/d14/star1.rkt |  2 ++
 2017/d14/test1.rkt |  2 ++
 3 files changed, 44 insertions(+)
 create mode 100644 2017/d14/main.rkt
 create mode 100644 2017/d14/star1.rkt
 create mode 100644 2017/d14/test1.rkt

diff --git a/2017/d14/main.rkt b/2017/d14/main.rkt
new file mode 100644
index 0000000..ec77cee
--- /dev/null
+++ b/2017/d14/main.rkt
@@ -0,0 +1,40 @@
+#lang reader "../aoc-lang.rkt"
+(require racket/sequence)
+(provide (rename-out [#%mb #%module-begin]))
+
+(define-macro (#%mb (STARS) (STR) ...)
+  #`(#%module-begin
+     ((if (eq? 'STARS '★) one-star (λ (x) #f)) (format "~a" 'STR)) ...))
+
+(define (one-star str)
+  (for*/sum ([i (in-range 128)]
+             [digit (in-list (kh->ints (knot-hash (format "~a-~a" str i))))])
+    digit))
+
+(define (kh->ints kh)
+  (for*/list ([c (in-string kh)]
+              [num (in-value (string->number (string c) 16))]
+              [c (in-string (~r num #:base 2 #:min-width 4 #:pad-string "0"))])
+    (string->number (string c))))
+
+(define (knot-hash seed-str [range-in 256])
+  (define ascii-chars (map char->integer (string->list seed-str)))
+  (define nums (reverse-segments range-in (append ascii-chars '(17 31 73 47 23)) #:reps 64))
+  (define dense-hash (for/list ([vals (in-slice 16 nums)])
+                       (apply bitwise-xor vals)))
+  (string-append* (for/list ([num (in-list dense-hash)])
+                    (~r num #:base 16 #:min-width 2 #:pad-string "0"))))
+
+(define (reverse-segments range-in lens #:reps [reps 1])
+  (define vec (list->vector (range range-in)))
+  (for*/fold ([current-position 0]
+              [skip-size 0])
+             ([rep (in-range reps)]
+              [len (in-list lens)])
+    (define posns (for/list ([i (in-range len)])
+                    (modulo (+ current-position i) range-in)))
+    (for ([val (in-list (map (curry vector-ref vec) posns))]
+          [posn (in-list (reverse posns))])
+      (vector-set! vec posn val))
+    (values (+ current-position len skip-size) (add1 skip-size)))
+  (vector->list vec))
\ No newline at end of file
diff --git a/2017/d14/star1.rkt b/2017/d14/star1.rkt
new file mode 100644
index 0000000..a05101d
--- /dev/null
+++ b/2017/d14/star1.rkt
@@ -0,0 +1,2 @@
+#lang reader "main.rkt" ★ ; 8214
+hxtvlmkl
\ No newline at end of file
diff --git a/2017/d14/test1.rkt b/2017/d14/test1.rkt
new file mode 100644
index 0000000..e2d998e
--- /dev/null
+++ b/2017/d14/test1.rkt
@@ -0,0 +1,2 @@
+#lang reader "main.rkt" ★ ; 8108
+flqrgnkx
\ No newline at end of file