aaronjeline · December 7, 2021 08:07 · Dec 7, 2021
diff --git a/7.rkt b/7.rkt
@@ -0,0 +1,86 @@
+#lang racket
+(require threading)
+
+(define sample-pos
+  (~>
+   "16,1,2,0,4,2,7,1,2,14"
+   #;
+   (with-input-from-file
+    "/tmp/input"
+    (λ () (port->string (current-input-port))))
+   string-trim
+   (string-split _ ",")
+   (map string->number _)))
+
+(define real-pos
+  (~>
+   (with-input-from-file
+    "/tmp/input"
+    (λ () (port->string (current-input-port))))
+   string-trim
+   (string-split _ ",")
+   (map string->number _)))
+
+(define (average lst)
+  (define sum (apply + lst))
+  (floor (/ sum (length lst))))
+
+(define memo (make-hash '()))
+
+(module+ test
+  (require rackunit))
+
+(define (indv-cost target at)
+  (define dist (abs (- target at)))
+  (define (f dist acc)
+    (if (zero? dist)
+        acc
+        (f (sub1 dist) (+ dist acc))))
+  (f dist 0))
+
+(module+ test
+  (check-equal? (indv-cost 16 5) 66)
+  (check-equal? (indv-cost 1 5) 10))
+
+
+(define (cost target lst)
+  (if (hash-has-key? memo target)
+      (hash-ref memo target)
+      (let* [
+             (result (apply + (map (λ (i) (indv-cost i target)) lst)))]
+        (begin
+          (hash-set! memo target result)
+          result))))
+(module+ test
+  (check-equal? (cost 5 sample-pos) 168)
+  (check-equal? (cost 2 sample-pos) 206))
+
+(define (list-range lst)
+  (define mx (foldl max (first lst) lst))
+  (define mn (foldl min (first lst) lst))
+  (in-range mn mx))
+
+(define start (average sample-pos))
+
+(define (go-left? target lst)
+  (< (cost (sub1 target) lst)
+     (cost target lst)))
+
+(define (go-right? target lst)
+  (< (cost (add1 target) lst)
+     (cost target lst)))
+
+(define (done? target lst)
+  (not (or (go-left? target lst) (go-right? target lst))))
+
+
+(define (step target lst)
+  (if (go-right? target lst)
+      (add1 target)
+      (sub1 target)))
+
+
+(define (loop target lst)
+  (if (done? target lst)
+      (cost target lst)
+      (loop (step target lst) lst)))