Initial data commit

Task/Sorting-algorithms-Patience-sort/Standard-ML/sorting-algorithms-patience-sort.ml

@@ -0,0 +1,55 @@
+structure PilePriority = struct
+  type priority = int
+  fun compare (x, y) = Int.compare (y, x) (* we want min-heap *)
+  type item = int list
+  val priority = hd
+end
+
+structure PQ = LeftPriorityQFn (PilePriority)
+
+fun sort_into_piles n =
+  let
+    val piles = DynamicArray.array (length n, [])
+    fun bsearch_piles x =
+      let
+        fun aux (lo, hi) =
+          if lo > hi then
+            lo
+          else
+            let
+              val mid = (lo + hi) div 2
+            in
+              if hd (DynamicArray.sub (piles, mid)) < x then
+                aux (mid+1, hi)
+              else
+                aux (lo, mid-1)
+            end
+      in
+        aux (0, DynamicArray.bound piles)
+      end
+    fun f x =
+      let
+        val i = bsearch_piles x
+      in
+        DynamicArray.update (piles, i, x :: DynamicArray.sub (piles, i))
+      end
+  in
+    app f n;
+    piles
+  end
+
+fun merge_piles piles =
+  let
+    val heap = DynamicArray.foldl PQ.insert PQ.empty piles
+    fun f (heap, acc) =
+      case PQ.next heap of
+        NONE => acc
+      | SOME (x::xs, heap') =>
+        f ((if null xs then heap' else PQ.insert (xs, heap')),
+           x::acc)
+  in
+    rev (f (heap, []))
+  end
+
+fun patience_sort n =
+  merge_piles (sort_into_piles n)