quicksort

Marko Tikvić
1 parent 69178b8246
Showing 1 changed file with 49 additions and 0 deletions Show diff stats
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
+}
...	...	@@ -0,0 +1,49 @@
	1	+package webutility
	2	+
	3	+type QSortDirection int
	4	+
	5	+const (
	6	+ QSortAscending = 0
	7	+ QSortDescending = 1
	8	+)
	9	+
	10	+// QuickSortable is an interface for quicksorting slices.
	11	+type QuickSortable interface {
	12	+ Swap(i, j int)
	13	+ Compare(i, j int) int
	14	+ Len() int
	15	+}
	16	+
	17	+// Quicksort quicksorts que.
	18	+func Quicksort(que QuickSortable, low, high int, dir QSortDirection) {
	19	+ if low >= high {
	20	+ return
	21	+ }
	22	+
	23	+ if dir != QSortAscending && dir != QSortDescending {
	24	+ return
	25	+ }
	26	+
	27	+ index := partition(que, low, high, dir)
	28	+ Quicksort(que, low, index-1, dir)
	29	+ Quicksort(que, index+1, high, dir)
	30	+}
	31	+
	32	+func partition(que QuickSortable, low, high int, dir QSortDirection) int {
	33	+ i := low - 1
	34	+ for j := low; j <= high-1; j++ {
	35	+ if dir == QSortAscending {
	36	+ if que.Compare(j, high) == -1 {
	37	+ i++
	38	+ que.Swap(i, j)
	39	+ }
	40	+ } else if dir == QSortDescending {
	41	+ if que.Compare(j, high) == 1 {
	42	+ i++
	43	+ que.Swap(i, j)
	44	+ }
	45	+ }
	46	+ }
	47	+ que.Swap(i+1, high)
	48	+ return i + 1
	49	+}
...	...