aoc

commit 87d7371ffa8a1555264aecc8d4a80d764f9479dc (patch)
parent b2fd306d964d4386e1e8dae54637fd93a0e35071
Author: Alex Karle <alex@alexkarle.com>
Date:   Thu,  8 Dec 2022 22:48:34 -0500

day8: Add part 2, unoptimized

Diffstat:
M
2022/08/sol.scm
 | 
55
++++++++++++++++++++++++++++++++++++++++++++++---------

1 file changed, 46 insertions(+), 9 deletions(-)
diff --git a/2022/08/sol.scm b/2022/08/sol.scm
@@ -37,22 +37,59 @@
             (max-in-dir? grid r c -1 0)
             (max-in-dir? grid r c 0 -1)))))
 
+(define (num-in-dir grid r c dr dc)
+  (let ((tree (grid-get grid r c))
+        (n (vector-length grid)))
+    (let loop ((r r) (c c) (count 0))
+      (let ((nr (+ r dr)) (nc (+ c dc)))
+        (if (or (neg? nr) (neg? nc)
+                (>= nr n) (>= nc n))
+            count ; made it off the map
+            (if (<= tree (grid-get grid nr nc))
+                (add1 count)
+                (loop nr nc (add1 count))))))))
+
+(define (score grid r c)
+  ; (print "visiting " r " " c)
+  (apply *
+        (filter (lambda (x) (> x 0))
+                (list (num-in-dir grid r c 0 1)
+                      (num-in-dir grid r c 1 0)
+                      (num-in-dir grid r c -1 0)
+                      (num-in-dir grid r c 0 -1)))))
+
 (define (range n)
   (if (equal? n 0)
       '(0)
       (append (range (sub1 n)) (list n))))
 
+(define (filter pred lst)
+  (if (null? lst)
+      '()
+      (if (pred (car lst))
+          (cons (car lst) (filter pred (cdr lst)))
+          (filter pred (cdr lst)))))
+
+(define (count-visible grid)
+  (let ((n (sub1 (vector-length grid))))
+    (let rloop ((r 0) (count 0))
+      (if (> r n)
+          count
+          (rloop (add1 r)
+                 (+ count (length (filter (lambda (c) (is-visible? grid r c))
+                                          (range n)))))))))
+
+(define (best-view grid)
+  (let ((n (sub1 (vector-length grid))))
+    (apply max (map (lambda (r)
+                      (apply max (map (lambda (c) (score grid r c)) (range n))))
+                    (range n)))))
+
 (define (main args)
   (let* ((lines (read-lines))
-         (grid (lines->grid lines))
-         (n (sub1 (length lines))))
-    (let ((visible (map
-                     (lambda (r)
-                        (map (lambda (c) (if (is-visible? grid r c) 1 0))
-                             (range n)))
-                     (range n))))
-      ; (for-each print visible)
-      (print (apply + (map (lambda (l) (apply + l)) visible))))))
+         (grid (lines->grid lines)))
+    (print (count-visible grid))
+    (print (best-view grid))))
 
 ;; for repl exploration
 (define gd '#(#(3 0 3 7 3)