update

Task/Sorting-algorithms-Merge-sort/Racket/sorting-algorithms-merge-sort-1.rkt

@@ -0,0 +1,15 @@
+#lang racket
+
+(define (merge xs ys)
+  (cond [(empty? xs) ys]
+        [(empty? ys) xs]
+        [(match* (xs ys)
+           [((list* a as) (list* b bs))
+            (cond [(<= a b) (cons a (merge as ys))]
+                  [         (cons b (merge xs bs))])])]))
+
+(define (merge-sort xs)
+  (match xs
+    [(or (list) (list _)) xs]
+    [_ (define-values (ys zs) (split-at xs (quotient (length xs) 2)))
+       (merge (merge-sort ys) (merge-sort zs))]))

Task/Sorting-algorithms-Merge-sort/Racket/sorting-algorithms-merge-sort-2.rkt

@@ -0,0 +1,19 @@
+#lang racket
+
+(define (merge-sort xs)
+  (merge* (map list xs)))
+
+(define (merge* xss)
+  (match xss
+    [(list)    '()]
+    [(list xs) xss]
+    [(list xs ys zss ...)
+     (merge* (cons (merge xs ys) (merge* zss)))]))
+
+(define (merge xs ys)
+  (cond [(empty? xs) ys]
+        [(empty? ys) xs]
+        [(match* (xs ys)
+           [((list* a as) (list* b bs))
+            (cond [(<= a b) (cons a (merge as ys))]
+                  [         (cons b (merge xs bs))])])]))