From a017ee87f224d8fd20b370e4034a0159fbb4c115 Mon Sep 17 00:00:00 2001
From: Oscar Najera <hi@oscarnajera.com>
Date: Sat, 17 Dec 2022 12:54:02 +0100
Subject: Day 15 CL eg monitor cover

---
 AoC2022/15/solver.lisp | 61 +++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 45 insertions(+), 16 deletions(-)

(limited to 'AoC2022')

diff --git a/AoC2022/15/solver.lisp b/AoC2022/15/solver.lisp
index 3d4fafd..0166b23 100644
--- a/AoC2022/15/solver.lisp
+++ b/AoC2022/15/solver.lisp
@@ -1,13 +1,6 @@
 (ql:quickload '(fiveam str cl-ppcre arrows uiop))
 
 
-(setf markers
-      (loop for line in (uiop:read-file-lines "eg-in")
-            for (sx sy bx by) = (multiple-value-bind (match values)
-                                    (cl-ppcre:scan-to-strings "Sensor at x=(-?\\d+), y=\(-?\\d+\): closest beacon is at x=(-?\\d+), y=(-?\\d+)"
-                                                              line)
-                                  (map 'list #'parse-integer values))
-            nconc (list (cons sx sy) (cons bx by))))
 
 (defun bounds (markers)
   (list (list
@@ -28,6 +21,13 @@
         (when (and (<= xmin x xmax) (<= ymin y ymax))
           (+ (- x xmin) (* (- y ymin) stride)))))))
 
+(defun from-grid (bounds)
+  (destructuring-bind ((xmin xmax) (ymin _)) bounds
+    (declare (ignore _))
+    (let ((stride (- xmax xmin -1)))
+      (lambda (pos)
+        (multiple-value-bind (y x) (floor pos stride)
+          (cons (+ x xmin) (+ y ymin)))))))
 
 (defun draw-grid (grid stride)
   (let ((out (make-string-output-stream)))
@@ -37,17 +37,46 @@
                     (princ (case elt
                              (0 ".")
                              (1 "S")
-                             (2 "B")) out)))
+                             (2 "B")
+                             (3 "#")) out)))
     (get-output-stream-string out)))
 
-(let* ((bounds (bounds markers))
+(defun manhattan-dist (pos-sensor pos-beacon)
+  (destructuring-bind ((sx . sy) (bx . by)) (list pos-sensor pos-beacon)
+    (+ (abs (- bx sx)) (abs (- by sy)))))
+
+(defun markers (lines)
+  (loop for line in lines
+        for (sx sy bx by) = (multiple-value-bind (match values)
+                                (cl-ppcre:scan-to-strings "Sensor at x=(-?\\d+), y=\(-?\\d+\): closest beacon is at x=(-?\\d+), y=(-?\\d+)"
+                                                          line)
+                                (declare (ignore match))
+                              (map 'list #'parse-integer values))
+        nconc (list (cons sx sy) (cons bx by))))
+
+
+(let* ((lines (uiop:read-file-lines "eg-in"))
+       (markers (markers lines))
+       (bounds (bounds markers))
        (loc (in-grid bounds))
-       (grid (grid bounds)))
+       (grid (grid bounds))
+       (coords (from-grid bounds)))
   (loop for ((sx . sy) (bx . by)) on markers by #'cddr
-        do (progn (princ (list sx sy bx by))
-                  (setf (aref grid (funcall loc sx sy)) 1)
+        do (progn (setf (aref grid (funcall loc sx sy)) 1)
                   (setf (aref grid (funcall loc bx by)) 2)))
-  (destructuring-bind ((xmin xmax) a) bounds
-    (princ (draw-grid grid (- xmax xmin -1)))
-    )
-  )
+
+  (loop for (sensor beacon) on markers by #'cddr
+        for distance = (manhattan-dist sensor beacon)
+        do (loop
+             for elt across grid
+             and l from 0
+             when (and (<= (manhattan-dist sensor (funcall coords l)) distance) (= elt 0))
+               do (setf (aref grid l) 3)))
+
+  (destructuring-bind ((xmin xmax) (ymin ymax)) bounds
+    (let ((stride (- xmax xmin -1)))
+      ;; (princ (draw-grid grid stride))
+      (loop repeat stride
+            for l from (* (+ 10 ymin) stride)
+            when (= 3 (aref grid l))
+              count it))))
-- 
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