From 84543a02b292c5be658f2b191377091affc4ef3d Mon Sep 17 00:00:00 2001
From: "marko.tikvic" <marko.tikvic@to-net.rs>
Date: Tue, 10 Sep 2019 15:43:17 +0200
Subject: [PATCH] quicksort

---
 quicksort.go | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 quicksort.go

diff --git a/quicksort.go b/quicksort.go
new file mode 100644
index 0000000..ba627fb
--- /dev/null
+++ b/quicksort.go
@@ -0,0 +1,49 @@
+package webutility
+
+type QSortDirection int
+
+const (
+	QSortAscending  = 0
+	QSortDescending = 1
+)
+
+// QuickSortable is an interface for quicksorting slices.
+type QuickSortable interface {
+	Swap(i, j int)
+	Compare(i, j int) int
+	Len() int
+}
+
+// Quicksort quicksorts que.
+func Quicksort(que QuickSortable, low, high int, dir QSortDirection) {
+	if low >= high {
+		return
+	}
+
+	if dir != QSortAscending && dir != QSortDescending {
+		return
+	}
+
+	index := partition(que, low, high, dir)
+	Quicksort(que, low, index-1, dir)
+	Quicksort(que, index+1, high, dir)
+}
+
+func partition(que QuickSortable, low, high int, dir QSortDirection) int {
+	i := low - 1
+	for j := low; j <= high-1; j++ {
+		if dir == QSortAscending {
+			if que.Compare(j, high) == -1 {
+				i++
+				que.Swap(i, j)
+			}
+		} else if dir == QSortDescending {
+			if que.Compare(j, high) == 1 {
+				i++
+				que.Swap(i, j)
+			}
+		}
+	}
+	que.Swap(i+1, high)
+	return i + 1
+}
-- 
1.8.1.2