Data commit

Task/Topswops/Racket/topswops.rkt

@@ -0,0 +1,17 @@
+#lang racket
+
+(define (all-misplaced? l)
+  (for/and ([x (in-list l)] [n (in-naturals 1)]) (not (= x n))))
+
+(define (topswops n)
+  (for/fold ([m 0]) ([p (in-permutations (range 1 (add1 n)))]
+                     #:when (all-misplaced? p))
+    (let loop ([p p] [n 0])
+      (if (= 1 (car p))
+        (max n m)
+        (loop (let loop ([l '()] [r p] [n (car p)])
+                (if (zero? n) (append l r)
+                    (loop (cons (car r) l) (cdr r) (sub1 n))))
+              (add1 n))))))
+
+(for ([i (in-range 1 11)]) (printf "~a\t~a\n" i (topswops i)))