aoc

commit 884cee487d779ed14ea96b750dbec86ba85bf9a0 (patch)
parent 486b135a0aabd6544748c50152121da0e31fb2bf
Author: Alex Karle <alex@alexkarle.com>
Date:   Wed, 14 Dec 2022 23:22:50 -0500

day14: Add part 2 solution (slow, but works)

Diffstat:
M
2022/14/sol.scm
 | 
32
++++++++++++++++++++++++++++++--

1 file changed, 30 insertions(+), 2 deletions(-)
diff --git a/2022/14/sol.scm b/2022/14/sol.scm
@@ -78,6 +78,23 @@
 	(else
 	 (hash-table-set! G (list x y) 'o))))
 
+(define (empty-incl-floor? G x y floor)
+  (not (or (hash-table-exists? G (list x y))
+	   (= y floor))))
+
+(define (drop-sand-floor G x y floor)
+  (cond ((empty-incl-floor? G x (add1 y) floor)
+	 (drop-sand-floor G x (add1 y) floor))
+	; we're blocked at this point, try left/right
+	((empty-incl-floor? G (sub1 x) (add1 y) floor)
+	 (drop-sand-floor G (sub1 x) (add1 y) floor))
+	((empty-incl-floor? G (add1 x) (add1 y) floor)
+	 (drop-sand-floor G (add1 x) (add1 y) floor))
+	(else
+	 (if (and (= x 500) (= y 0))
+	     #f  ; plugged the start -> done
+	     (hash-table-set! G (list x y) 'o)))))
+
 ;; We map the world state as a hash table (effectively a sparse matrix)
 ;; so that we don't have to guess the vector dimensions first
 (define (main args)
@@ -87,14 +104,25 @@
 		(for-each (lambda (pt)
 			    (hash-table-set! G pt 'R)) (parse-line l)))
 	      lines)
-    (let ((cliff (apply max (map (lambda (pt) (cadr pt)) (hash-table-keys G)))))
+    (let* ((cliff (apply max (map (lambda (pt) (cadr pt)) (hash-table-keys G))))
+	   (floor (+ 2 cliff)))
       ;; note: could also just count the number of 'o values instead of i
       (let loop ((i 0))
 	; (print "------" i "-------")
 	; (print-grid G)
 	(if (drop-sand G 500 0 cliff)
 	    (loop (add1 i))
-	    (print i))))))
+	    ;; HACK: we can keep the same grid, since we stopped RIGHT at the point
+	    ;; we'd hit the floor anyways--just make sure to sum your numbers together!
+	    (let floop ((j 0))
+	      ;; (print "------" j "-------")
+	      ;; (print-grid G)
+	      (if (drop-sand-floor G 500 0 floor)
+		  (floop (add1 j))
+		  (begin
+		    (print i)
+		    (print (+ i (add1 j)))))))))
+      (print-grid G)))
 
 ; For repl
 (define ls '("498,4 -> 498,6 -> 496,6"