From 8f291992bdd98bd7ca6eefe084790e56d00833a8 Mon Sep 17 00:00:00 2001
From: Paul Buetow <paul@buetow.org>
Date: Fri, 17 Jul 2020 09:03:52 +0100
Subject: fix shell sort

---
 ds/comparer.go    |  4 ++++
 sort/sort_test.go | 17 +++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/ds/comparer.go b/ds/comparer.go
index 8fb3727..c132ea9 100644
--- a/ds/comparer.go
+++ b/ds/comparer.go
@@ -8,3 +8,7 @@ type Comparer interface {
 	HigherEqual(a Comparer) bool
 	Int() int
 }
+
+func (c []Comparer) firstN(n int) []Comparer {
+	return c
+}
diff --git a/sort/sort_test.go b/sort/sort_test.go
index 9593cde..00f056a 100644
--- a/sort/sort_test.go
+++ b/sort/sort_test.go
@@ -33,6 +33,12 @@ func TestShellSort(t *testing.T) {
 	}
 }
 
+func TestShuffleSort(t *testing.T) {
+	for i := 1; i <= maxLength; i *= 10 {
+		testShuffle(Shuffle, i, t)
+	}
+}
+
 func BenchmarkInsertionSort(b *testing.B) {
 	for i := 1; i <= maxLength; i *= 10 {
 		benchmark(Insertion, i, b)
@@ -63,6 +69,17 @@ func test(sort sortAlgorithm, length int, t *testing.T) {
 	t.Run(fmt.Sprintf("%d", length), cb)
 }
 
+func testShuffle(sort sortAlgorithm, length int, t *testing.T) {
+	cb := func(t *testing.T) {
+		t.Parallel()
+		a := sort(ds.SortedIntegers(length))
+		if Sorted(a) {
+			t.Errorf("Array sorted: %v", a)
+		}
+	}
+	t.Run(fmt.Sprintf("%d", length), cb)
+}
+
 func benchmark(sort sortAlgorithm, length int, b *testing.B) {
 	cb := func(b *testing.B) {
 		a := makeIntegers(length, length)
-- 
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