refactor from c to racket

1 files changed, 106 insertions, 0 deletions

diff --git a/advent-of-code/2023/03/2.rkt b/advent-of-code/2023/03/2.rkt
new file mode 100644
index 0000000..721a9d1
--- /dev/null
+++ b/advent-of-code/2023/03/2.rkt
@@ -0,0 +1,106 @@
+#lang racket
+
+(require "../lib/utils.rkt")
+(require "../lib/obj.rkt")
+
+(define (read-input)
+  (call-with-input-file "input"
+    (lambda (fp) 
+      (list->vector (get-lines fp)))))
+
+(define schema (read-input))
+
+(define (char-at line col)
+  (string-ref (vector-ref schema line) col))
+
+(define height (vector-length schema))
+(define width (string-length (vector-ref schema 0)))
+
+(define make-num (obj-maker 'line 'col 'value 'length))
+
+(define (scan-nums)
+  (define nums '())
+  (let loop ((i 0))
+    (if (>= i height)
+      (void)
+      (let ()
+        (let loop ((j 0))
+            (define curline (vector-ref schema i))
+            (if (>= j width)
+            (void)
+            (let ()
+                (define next 1)
+                (define (find-next)
+                  (if (or (>= (+ j next) 140)
+                          (not (char-numeric? (char-at i (+ j next)))))
+                    (void)
+                    (let ()
+                      (set! next (+ 1 next))
+                      (find-next))))
+                (if (char-numeric? (char-at i j))
+                  (let ()
+                    (find-next)
+                    (define value (string->number (substring curline j (+ j next))))
+                    (set! nums (cons (make-num i j value next) nums)))
+                  (void))
+                (loop (+ j next)))))
+        (loop (+ 1 i)))))
+  (reverse nums))
+(define nums (scan-nums))
+
+(define (is-symbol? c)
+  (and (not (char-numeric? c))
+       (not (char=? #\. c))))
+
+(define (collect-adjacent-positions num)
+  (define (position-range line start end)
+    (define delta (- end start))
+    (map list (repeat delta line) (range start end)))
+  (define left
+    (if (= 0 (num 'col))
+      '()
+      (list (list (num 'line) (- (num 'col) 1)))))
+  (define right
+    (if (= width (+ (num 'col) (num 'length)))
+      '()
+      (list (list (num 'line) (+ (num 'col) (num 'length))))))
+  (define up
+    (if (= 0 (num 'line))
+      '()
+      (position-range (- (num 'line) 1)
+                      (max 0 (- (num 'col) 1))
+                      (min width (+ (num 'col) (num 'length) 1)))))
+  (define down
+    (if (= (- height 1) (num 'line))
+      '()
+      (position-range (+ (num 'line) 1)
+                      (max 0 (- (num 'col) 1))
+                      (min width (+ (num 'col) (num 'length) 1)))))
+  (append left right up down))
+
+(define asterisks (make-hash))
+
+(define (mark-adj-asterisk num)
+  (define adjs (collect-adjacent-positions num))
+  (define (mark coord)
+    (if (not (char=? #\* (char-at (car coord) (cadr coord))))
+      (void)
+      (let ()
+        (when (not (hash-has-key? asterisks coord))
+          (hash-set! asterisks coord '()))
+        (hash-set! asterisks coord (cons (num 'value) (hash-ref asterisks coord))))))
+  (for-each mark adjs))
+
+(for-each mark-adj-asterisk nums)
+
+(define aster-list (hash->list asterisks))
+
+(define (is-gear? aster)
+  (define nums-list (cdr aster))
+  (= 2 (length nums-list)))
+
+(define (power aster)
+  (define nums-list (cdr aster))
+  (* (car nums-list) (cadr nums-list)))
+
+(apply + (map power (filter is-gear? aster-list)))