From de2cfb93f12cf2b6e6b7575540c3061f210fb4e6 Mon Sep 17 00:00:00 2001
From: Oscar Najera <hi@oscarnajera.com>
Date: Fri, 29 Dec 2023 20:59:07 +0100
Subject: refactor

---
 AoC2023/day20/solver.lisp | 71 ++++++++++++++++++++++++-----------------------
 1 file changed, 37 insertions(+), 34 deletions(-)

(limited to 'AoC2023/day20/solver.lisp')

diff --git a/AoC2023/day20/solver.lisp b/AoC2023/day20/solver.lisp
index d57af9a..21b0bed 100644
--- a/AoC2023/day20/solver.lisp
+++ b/AoC2023/day20/solver.lisp
@@ -3,34 +3,38 @@
   (:use :cl :fiveam :alexandria))
 (in-package :day20)
 
-(defstruct module
+(defstruct (module (:constructor mk-module
+                       (type outputs
+                        &aux (state (if (eq type 'conjunction)
+                                        (make-hash-table) 'off)))))
   type state outputs)
 
+(defun prepare-board (board)
+  "Records into every conjunction which are its inputs."
+  (maphash (lambda (name value)
+             (with-slots (type state outputs) value
+               (dolist (out outputs)
+                 (when (arrows:some->
+                        (gethash out board)
+                        (module-type)
+                        (eq 'conjunction))
+                   (setf (gethash name (module-state (gethash out board))) 'low)))))
+           board))
+
 (defun parse-input (lines)
   (let ((board (make-hash-table)))
-    (dolist (instruction lines board)
+    (dolist (instruction lines)
       (destructuring-bind (module outputs) (str:split " -> " instruction)
         (let ((outputs (mapcar #'read-from-string (str:split ", " outputs)))
-              (name (if (string-equal "broadcaster" module) 'broadcaster (read-from-string (subseq module 1))))
+              (name (if (string-equal "broadcaster" module) 'broadcaster
+                        (read-from-string (subseq module 1))))
               (type (ecase (elt module 0)
                       (#\b 'broadcaster)
                       (#\& 'conjunction)
                       (#\% 'flip-flop))))
-          (setf (gethash name board) (make-module :type type
-                                                  :state (if (eq type 'conjunction) (make-hash-table) 'off)
-                                                  :outputs outputs)))))))
-
-(defun prepare-board (board)
-  (maphash (lambda (name value)
-             (with-slots (type state outputs) value
-               (dolist (out outputs)
-                 (when (arrows:some->
-                        (gethash out board)
-                        (slot-value 'type)
-                        (eq 'conjunction))
-                   (setf (gethash name (slot-value (gethash out board) 'state)) 'low)))))
-           board)
-  board)
+          (setf (gethash name board) (mk-module type outputs)))))
+    (prepare-board board)
+    board))
 
 (defun toggle (state)
   (ecase state
@@ -61,7 +65,7 @@
    signals))
 
 (test parts
-  (let ((board (prepare-board (parse-input (uiop:read-file-lines "eg-i1")))))
+  (let ((board (parse-input (uiop:read-file-lines "eg-i1"))))
     (is (equal
          '((BROADCASTER A LOW) (BROADCASTER B LOW) (BROADCASTER C LOW))
          (propagate board '((button broadcaster low)))))
@@ -74,7 +78,7 @@
     (is (null (propagate board '((c blank low)))))))
 
 (defun solver1 (lines)
-  (let ((board (prepare-board (parse-input lines))))
+  (let ((board (parse-input lines)))
     (labels ((rec (signals n-high n-low)
                (if (null signals)
                    (list n-high n-low)
@@ -91,7 +95,8 @@
   (apply #'lcm (mapcar #'cdr cycles)))
 
 (defun solver2 ()
-  (let* ((board (prepare-board (parse-input (uiop:read-file-lines "input"))))
+  (let* ((board (parse-input (uiop:read-file-lines "input")))
+         (start '((button broadcaster low)))
          ;; feed is a single conjunction that gives to rx by inspecting input
          ;; feed has 4 inputs, it needs them all to be on high before it outputs
          ;; a low for rx
@@ -100,28 +105,26 @@
          ;; their cycle.
          (feed (loop for name being the hash-key of board
                        using (hash-value module)
-                     when (member 'rx (slot-value module 'outputs))
+                     when (member 'rx (module-outputs module))
                        return name))
-         (cycles (loop for name being the hash-key of board
-                         using (hash-value module)
-                       when (member feed (slot-value module 'outputs))
-                         collect (cons name 0)))
-         (presses 1)
-         (start '((button broadcaster low))))
+         cycles)
+
+    (maphash (lambda (name module)
+               (when (member feed (module-outputs module))
+                 (push (cons name nil) cycles)))
+             board)
 
     (loop named outer
           for signals = (propagate board start) then (propagate board (or signals start))
-          when (null signals)
-            do (incf presses)
-               ;; until (< 4000 presses)
+          count (null signals) into presses
+          ;; until (< 4000 presses)
           do
              (loop for (from to pulse) in signals do
                (when (and (eq to feed) (eq pulse 'high))
-                 (setf (cdr (assoc from cycles)) presses))
-               (when (every (compose #'positive-fixnum-p #'cdr) cycles)
+                 (setf (cdr (assoc from cycles)) (1+ presses)))
+               (when (every (compose #'numberp #'cdr) cycles)
                  (return-from outer (common-cycle cycles)))))))
 
-
 (test solutions
   (is (= 32000000 (solver1 (uiop:read-file-lines "eg-i1"))))
   (is (= 11687500 (solver1 (uiop:read-file-lines "eg-i2"))))
-- 
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