Day 15: Done finally.

src/15-wrong.rkt

@@ -1,39 +0,0 @@
-#lang curly-fn racket
-
-(require "../lib.rkt")
-
-(define input
-  (for/vector ([row (problem-input 15)])
-    (for/vector ([col (string->list row)])
-      (char->number col))))
-
-(define dim (vector-length input))
-
-(define (grid-ref dim row col)
-  (define row* (remainder row dim))
-  (define col* (remainder col dim))
-  (define offset (+ (quotient row dim) (quotient col dim)))
-  (define v (+ offset (vector-ref (vector-ref input row*) col*)))
-  (if (> v 9) (add1 (% v 10)) v))
-
-(define (adjs dim row col)
-  (filter #{and (<= 0 (car %) (sub1 dim)) (<= 0 (cdr %) (sub1 dim))}
-          `((,(add1 row) . ,col) (,(sub1 row) . ,col) (,row . ,(add1 col)) (,row . ,(sub1 col)))))
-
-(define (find-shortest-path-weight dim)
-  (for/fold ([weights (hash '(0 . 0) 0)]
-             #:result (hash-ref weights `(,(sub1 dim) . ,(sub1 dim))))
-            ([diag (range* 0 (+ dim dim))])
-    (for/fold ([weights weights])
-              ([row (range* 0 diag  1)]
-               [col (range* diag 0 -1)]
-               #:when (and (< row dim) (< col dim)))
-      (for/fold ([weights weights])
-                ([adj (adjs dim row col)])
-        (match-let* ([(cons row* col*) adj]
-                     [weight (+ (grid-ref dim row* col*)
-                                (hash-ref weights (cons row col)))])
-          (hash-update weights adj #{if (< weight %) weight %} +inf.0))))))
-
-(show-solution (find-shortest-path-weight dim)
-               (find-shortest-path-weight (* dim 5)))

src/15.rkt

@@ -0,0 +1,49 @@
+#lang curly-fn racket
+
+(require graph
+         (except-in "../lib.rkt" transpose))
+
+(define input
+  (for/vector ([row (problem-input 15)])
+    (for/vector ([col (string->list row)])
+      (char->number col))))
+
+(define dim (vector-length input))
+
+(define (grid-ref row col)
+  (define row* (remainder row dim))
+  (define col* (remainder col dim))
+  (define offset (+ (quotient row dim) (quotient col dim)))
+  (define v (+ offset (vector-ref (vector-ref input row*) col*)))
+  (if (> v 9) (add1 (% v 10)) v))
+
+(define (adjs dim row col)
+  (filter #{and (<= 0 (car %) (sub1 dim)) (<= 0 (cdr %) (sub1 dim))}
+          `((,(add1 row) . ,col) (,(sub1 row) . ,col) (,row . ,(add1 col)) (,row . ,(sub1 col)))))
+
+(for/fold ([weights (hash '(0 . 0) 0)]
+           #:result (printf "Part 1: ~a\n" (hash-ref weights `(,(sub1 dim) . ,(sub1 dim)))))
+          ([diag (range* 0 (+ dim dim))])
+  (for/fold ([weights weights])
+            ([row (range* 0 diag  1)]
+             [col (range* diag 0 -1)]
+             #:when (and (< row dim) (< col dim)))
+    (for/fold ([weights weights])
+              ([adj (adjs dim row col)])
+      (match-let* ([(cons row* col*) adj]
+                   [weight (+ (grid-ref row* col*)
+                              (hash-ref weights (cons row col)))])
+        (hash-update weights adj #{if (< weight %) weight %} +inf.0)))))
+
+(define (make-graph dim)
+  (define graph (weighted-graph/directed '()))
+  (for* ([row (range dim)]
+         [col (range dim)]
+         [adj (adjs dim row col)])
+    (add-directed-edge! graph (cons row col) adj (grid-ref (car adj) (cdr adj))))
+  (displayln "Graph created.")
+  graph)
+
+(let*-values ([(dim) (* dim 5)]
+              [(weights paths) (dijkstra (make-graph dim) '(0 . 0))])
+  (printf "Part 2: ~a\n" (hash-ref weights `(,(sub1 dim) . ,(sub1 dim)))))