From 4175006ade55ab79fcde3deb5b7658d5fbfc05b3 Mon Sep 17 00:00:00 2001
From: Oscar Najera <hi@oscarnajera.com>
Date: Tue, 13 Dec 2022 01:28:52 +0100
Subject: have a struct

---
 AoC2022/12/solver.lisp | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

(limited to 'AoC2022/12/solver.lisp')

diff --git a/AoC2022/12/solver.lisp b/AoC2022/12/solver.lisp
index e00861a..b2a0752 100644
--- a/AoC2022/12/solver.lisp
+++ b/AoC2022/12/solver.lisp
@@ -1,5 +1,9 @@
 (ql:quickload '(fiveam uiop))
 
+(defstruct land
+  elevation
+  neighbors)
+
 (defun possible-directions (width height)
   ;; point on grid is p=x+y*width
   (lambda (pos)
@@ -21,31 +25,34 @@
                       (t (- (char-code chr) 96))))
        data))
 
-(defun next-steps (place candidates land paths)
-  (let ((elevation (aref land place)))
+(defun land (input-file)
+  (let ((data (uiop:read-file-lines input-file)))
+    (make-land :elevation (elevations (apply #'concatenate 'string data))
+               :neighbors (possible-directions (length (car data)) (length data)))))
+
+(defun next-steps (place land paths)
+  (let ((elevation (aref (land-elevation land) place)))
     (unless (= 27 elevation)
       (mapcan (lambda (option)
                 (when (and (not (gethash option paths))
-                           (>= (1+ elevation) (aref land option)))
+                           (>= (1+ elevation) (aref (land-elevation land) option)))
                   (setf (gethash option paths) (cons option (gethash place paths)))
                   (list option)))
-              (funcall candidates place)))))
+              (funcall (land-neighbors land) place)))))
 
-(defun shortest-path (starts candidates land paths)
-  (let ((next (mapcan (lambda (place) (next-steps place candidates land paths)) starts)))
+(defun shortest-path (starts land paths)
+  (let ((next (mapcan (lambda (place) (next-steps place land paths)) starts)))
     (when next
-      (shortest-path next candidates land paths))))
+      (shortest-path next land paths))))
 
 (defun solver (input-file start-p)
-  (let* ((data (uiop:read-file-lines input-file))
-         (candidates (possible-directions (length (car data)) (length data)))
-         (land (elevations (apply #'concatenate 'string data)))
+  (let* ((land (land input-file))
          (paths (make-hash-table :test #'eq))
-         (finish (position 27 land :test #'eq))
+         (finish (position 27 (land-elevation land) :test #'eq))
          (starts (loop for i from 0
-                       for el across land
+                       for el across (land-elevation land)
                        when (funcall start-p el) collect (progn (setf (gethash i paths) (list i)) i))))
-    (shortest-path starts candidates land paths)
+    (shortest-path starts land paths)
     (1- (length (gethash finish paths)))))
 
 (fiveam:test solver
-- 
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