insertion sort

sorting/insertion.go

@@ -0,0 +1,16 @@
+package sorting
+
+type insertion struct{}
+
+func (*insertion) Sort(items Sortable) {
+	len := items.Len()
+	for i := 1; i < len; i++ {
+		for j := i; j > 0 && items.Less(j, j-1); j-- {
+			items.Swap(j, j-1)
+		}
+	}
+}
+
+func NewInsertion() Sorter {
+	return &insertion{}
+}

sorting/sort_test.go

@@ -7,3 +7,19 @@ import (
 func TestSelection(t *testing.T) {
 	CheckSorter(NewSelection())
 }
+
+func BenchmarkSelection(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		BenchmarkSort(10000, NewSelection())
+	}
+}
+
+func TestInsertion(t *testing.T) {
+	CheckSorter(NewInsertion())
+}
+
+func BenchmarkInsertion(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		BenchmarkSort(10000, NewInsertion())
+	}
+}

sorting/testing.go

@@ -24,7 +24,7 @@ func SameInts(a, b []int) bool {
 func CheckSorter(s Sorter) {
 	rand.Seed(time.Now().Unix())
 
-	actual := rand.Perm(100)
+	actual := rand.Perm(1000)
 	expected := make([]int, len(actual))
 	copy(expected, actual)
 
@@ -35,3 +35,9 @@ func CheckSorter(s Sorter) {
 		log.Fatalf("wrong order:\n actual:\t%v\n expected:\t%v\n", actual, expected)
 	}
 }
+
+func BenchmarkSort(numItems int, s Sorter) {
+	rand.Seed(time.Now().Unix())
+	items := rand.Perm(numItems)
+	s.Sort(IntSort(items))
+}