Use List.append instead of List.prepend, and reverse the lists at the…

… end

exercises/practice/killer-sudoku-helper/.meta/Example.roc

@@ -10,18 +10,19 @@ combinations = \{ sum, size, exclude ? [] } ->
             else
 
         when digits is
-            [] -> [[]]
+            [] -> []
             [single] -> if single == target then [[single]] else []
             [first, .. as rest] ->
                 if first > target then
                     []
                     else
 
                 help (target - first) rest
-                |> List.map \combi -> combi |> List.prepend first
+                |> List.map \combi -> combi |> List.append first
                 |> List.concat (help target rest)
     availableDigits =
         [1, 2, 3, 4, 5, 6, 7, 8, 9]
         |> List.dropIf \digit -> exclude |> List.contains digit
     help sum availableDigits
     |> List.keepIf \combi -> List.len combi == size |> Num.toU64
+    |> List.map List.reverse