update

Task/Sorting-algorithms-Heapsort/Racket/sorting-algorithms-heapsort.rkt

@@ -0,0 +1,26 @@
+#lang racket
+(require (only-in srfi/43 vector-swap!))
+
+(define (heap-sort! xs)
+  (define (ref i) (vector-ref xs i))
+  (define (swap! i j) (vector-swap! xs i j))
+  (define size (vector-length xs))
+
+  (define (sift-down! r end)
+    (define c (+ (* 2 r) 1))
+    (define c+1 (+ c 1))
+    (when (<= c end)
+      (define child
+        (if (and (<= c+1 end) (< (ref c) (ref c+1)))
+            c+1 c))
+      (when (< (ref r) (ref child))
+        (swap! r child))
+      (sift-down! child end)))
+
+  (for ([i (in-range (quotient (- size 2) 2) -1 -1)])
+    (sift-down! i (- size 1)))
+
+  (for ([end (in-range (- size 1) 0 -1)])
+    (swap! 0 end)
+    (sift-down! 0 (- end 1)))
+  xs)