Initial data commit

Task/Shortest-common-supersequence/Racket/shortest-common-supersequence.rkt

@@ -0,0 +1,33 @@
+#lang racket
+
+(struct link (len letters))
+
+(define (link-add li n letter)
+  (link (+ n (link-len li))
+        (cons letter (link-letters li))))
+
+(define (memoize f)
+  (local ([define table (make-hash)])
+    (lambda args
+      (dict-ref! table args (λ () (apply f args))))))
+
+(define scs/list
+  (memoize
+   (lambda (x y)
+     (cond
+       [(null? x)
+        (link (length y) y)]
+       [(null? y)
+        (link (length x) x)]
+       [(eq? (car x) (car y))
+        (link-add (scs/list (cdr x) (cdr y)) 1 (car x))]
+       [(<= (link-len (scs/list x (cdr y)))
+            (link-len (scs/list (cdr x) y)))
+        (link-add (scs/list x (cdr y)) 1 (car y))]
+       [else
+        (link-add (scs/list (cdr x) y) 1 (car x))]))))
+
+(define (scs x y)
+  (list->string (link-letters (scs/list (string->list x) (string->list y)))))
+
+(scs "abcbdab" "bdcaba")