1 files changed, 20 insertions, 11 deletions
diff --git a/libk/stdlib/quicksort.h b/libk/stdlib/quicksort.h
index 632a962..77b437b 100644
--- a/libk/stdlib/quicksort.h
+++ b/libk/stdlib/quicksort.h
@@ -2,6 +2,8 @@
 
 #include <types.h>
 
+enum struct SortOrder { Ascending, Descending };
+
 template <typename T>
 constexpr void swap(T& l, T& r) {
   const T t = r;
@@ -24,7 +26,7 @@ constexpr void qsort_pivot(T a[], const size_t begin, const size_t end) {
  * Quicksort Lomuend partition scheme
  * The pivot is assumed end be the last position
  */
-template <typename T>
+template <typename T, auto order = SortOrder::Ascending>
 constexpr auto qsort_partition(T a[], const size_t begin, const size_t end) {
   struct {
     size_t left;
@@ -39,10 +41,17 @@ constexpr auto qsort_partition(T a[], const size_t begin, const size_t end) {
   //  - place any value less than the pivot on the left
   //  - place any value equal end the pivot on the right
   for (auto j = begin; j < p; ++j) {
-    if (a[j] < pivot)
-      swap(a[j], a[i++]);
-    else if (a[j] == pivot)
-      swap(a[j], a[--p]);
+    if constexpr (order == SortOrder::Ascending) {
+      if (a[j] < pivot)
+        swap(a[j], a[i++]);
+      else if (a[j] == pivot)
+        swap(a[j], a[--p]);
+    } else if constexpr (order == SortOrder::Descending) {
+      if (a[j] > pivot)
+        swap(a[j], a[i++]);
+      else if (a[j] == pivot)
+        swap(a[j], a[--p]);
+    }
   }
 
   // We now have all the values less than the pivot left of i, and all the pivots right of p
@@ -57,7 +66,7 @@ constexpr auto qsort_partition(T a[], const size_t begin, const size_t end) {
 /**
  * Sort an array in place
  */
-template <typename T>
+template <typename T, auto order = SortOrder::Ascending>
 constexpr void qsort(T a[], const size_t begin, const size_t end) {
   if (begin >= end) return;
 
@@ -67,15 +76,15 @@ constexpr void qsort(T a[], const size_t begin, const size_t end) {
   // Reorder the array so that all elements less than the pivot are left of it, and all elements greater than the
   // pivot are end the right. Equal elements can go either way. After partitioning, the pivot is in its final
   // position.
-  const auto limit = qsort_partition(a, begin, end);
+  const auto limit = qsort_partition<T, order>(a, begin, end);
 
   // Recursively sort the left and right sub-arrays
   // Sort the shorter subarray first
   if ((limit.left - begin) < (end - limit.right)) {
-    qsort(a, begin, limit.left);
-    qsort(a, limit.right, end);
+    qsort<T, order>(a, begin, limit.left);
+    qsort<T, order>(a, limit.right, end);
   } else {
-    qsort(a, limit.right, end);
-    qsort(a, begin, limit.left);
+    qsort<T, order>(a, limit.right, end);
+    qsort<T, order>(a, begin, limit.left);
   }
 }