From 62b4399322841a8fd5aa9dc0e63bf12fce683ee3 Mon Sep 17 00:00:00 2001
From: Gregory <neogen570@gmail.com>
Date: Tue, 14 Dec 2021 12:35:28 +0200
Subject: [PATCH] insertion sort

---
 sorting/insertion.go | 16 ++++++++++++++++
 sorting/sort_test.go | 16 ++++++++++++++++
 sorting/testing.go   |  8 +++++++-
 3 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 sorting/insertion.go

diff --git a/sorting/insertion.go b/sorting/insertion.go
new file mode 100644
index 0000000..ee13ad4
--- /dev/null
+++ b/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{}
+}
diff --git a/sorting/sort_test.go b/sorting/sort_test.go
index 24b6d0e..a45fca5 100644
--- a/sorting/sort_test.go
+++ b/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())
+	}
+}
diff --git a/sorting/testing.go b/sorting/testing.go
index b5ec50b..a7c08b3 100644
--- a/sorting/testing.go
+++ b/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))
+}