From 28881608de66d261672ec1f7b99bf867223d1a4b Mon Sep 17 00:00:00 2001
From: Peter Tillemans <pti@snamellit.com>
Date: Sun, 22 Dec 2024 13:46:27 +0100
Subject: [PATCH] solve day22 part 1 and 2

---
 src/2024/day22.lisp        | 98 +++++++++++++++++++++++++++++++++++---
 tests/2024/day22-test.lisp | 39 ++++++++++-----
 2 files changed, 120 insertions(+), 17 deletions(-)

diff --git a/src/2024/day22.lisp b/src/2024/day22.lisp
index f51dd94..163a9fb 100644
--- a/src/2024/day22.lisp
+++ b/src/2024/day22.lisp
@@ -1,18 +1,20 @@
 
 (defpackage :aoc/2024/22
-  (:use :cl :aoc :alexandria :trivia :lla)
+  (:use :cl :aoc :alexandria :lla :arrow-macros)
   (:export
    #:sample-data
    #:sample-data2
    #:part1
    #:part2
+   #:next-random
+   #:repeat-random
    ))
 
 (in-package :aoc/2024/22)
 
 
 (defun parse-line (line)
-  line)
+  (parse-integer line))
 
 
 (defun parse-input (lines)
@@ -21,15 +23,99 @@
 (defparameter input-text (test-input 2024 22))
 (defparameter input-data (parse-input input-text))
 
-(defparameter sample-text (aoc:split-lines ""))
+(defparameter sample-text (aoc:split-lines "1
+10
+100
+2024
+"))
+
 (defparameter sample-data 
-              (parse-input sample-text))
+  (parse-input sample-text))
+
+(defparameter PRUNE (ash 1 24))
+(defun rnd-step (n d)
+  (mod (logxor n (ash n d)) PRUNE))
+
+(defun next-random (n)
+  (-> n
+    (rnd-step 6)
+    (rnd-step -5)
+    (rnd-step 11)))
+
+(defun repeat-random (seed n)
+  (loop
+    for i from 1 to n
+    do (setf seed (next-random seed))
+    finally (return seed)))
 
 (defun part1 (data)
-  (length data))
+  (loop
+    for buyer in data
+    sum (repeat-random buyer 2000)))
+
+(defun day-prices (seed)
+  (make-array '(2001)
+	      :initial-contents
+	      (loop
+		for i from 1 to 2001
+		collect (mod seed 10)
+		do (setf seed (next-random seed))
+		)
+	      
+	      ))
+
+(defun sum-table (a b)
+  (loop
+    for i from 0 below (array-total-size a)
+    for x = (aref b i)
+    if (plusp x)
+      do (incf (aref a i) x))
+  as)
+
+(defun make-diff (prices)
+  (let ((diffs (copy-array prices)))
+    (loop
+      for i from 1 below (array-dimension prices 0)
+      do (decf (aref diffs i) (aref prices (1- i))))
+    diffsG))
+
+(defun make-buyer-table (seed)
+  (let* ((prices (day-prices seed))
+	 (diffs (make-diff prices))
+	 (buyer-table (make-array (list 19 19 19 19) :initial-element -1)))
+    
+    (loop
+      for i from 4 below (array-dimension prices 0)
+      for p = (aref prices i) 
+      for d1 = (+ 9 (aref diffs i))
+      for d2 = (+ 9 (aref diffs (1- i)))
+      for d3 = (+ 9 (aref diffs (- i 2)))
+      for d4 = (+ 9 (aref diffs (- i 3)))
+      for bp = (aref buyer-table d1 d2 d3 d4)
+      if (minusp bp)
+	do (setf (aref buyer-table d1 d2 d3 d4) p))
+    buyer-table))
+
+(defun price-diff-table (seeds)
+  (let ((table (make-array (list 19 19 19 19) :initial-element 0)))
+    (loop
+      for buyer from 0
+      for s in seeds
+      do (sum-table table (make-buyer-table s)))
+    table))
+
+(defun maxtable (table)
+  (loop
+    for i from 0 below (array-total-size table)
+    maximize (row-major-aref table i)))
+
+
+
+
+(defparameter sample-data2 '(1 2 3 2024))
 
 (defun part2 (data)
-  (length data))
+  (maxtable (price-diff-table data)))
 
 (defun solve-day ()
   (format t "part1: ~A~%" (part1 input-data))
diff --git a/tests/2024/day22-test.lisp b/tests/2024/day22-test.lisp
index fa9b6e9..28f9c60 100644
--- a/tests/2024/day22-test.lisp
+++ b/tests/2024/day22-test.lisp
@@ -7,21 +7,38 @@
                                         ;:parent suite-2024
              )
 
-(define-test test-foo
-             :parent suite-2024-22
-             ) 
+(define-test test-next-random
+  :parent suite-2024-22
+  (let ((rnd 123))
+    (loop
+      for expected in '(15887950
+			16495136
+			527345
+			704524
+			1553684
+			12683156
+			11100544
+			12249484
+			7753432
+			5908254)
+      do (setf rnd (next-random rnd))
+      do (is = expected rnd)))) 
 
 
-(define-test test-bar
-             :parent suite-2024-22
-             )
-
+(define-test test-buyers-end-of-day
+  :parent suite-2024-22
+  (loop
+    for buyer in '((1 . 8685429)
+		   (10 . 4700978)
+		   (100 . 15273692)
+		   (2024 . 8667524))
+    do (is = (cdr buyer) (repeat-random (car buyer) 2000))))
 
 
 (define-test+run test-part1
-                 :parent suite-2024-22
-                 (is equal nil (part1 sample-data)))
+  :parent suite-2024-22
+  (is equal 37327623 (part1 sample-data)))
 
 (define-test+run test-part2
-                 :parent suite-2024-22
-                 (is equal nil (part2 sample-data)))
+  :parent suite-2024-22
+  (is equal 23 (part2 sample-data2)))