From 43e0ca7edfa491dcb1e92cef4f421c93d0eacacb Mon Sep 17 00:00:00 2001
From: dudaodong <lanliddd.2007@163.com>
Date: Fri, 14 Jan 2022 18:17:46 +0800
Subject: [PATCH] feat: add ShellSort

---
 algorithm/sorter.go      | 27 ++++++++++++++++++++++++++-
 algorithm/sorter_test.go | 13 +++++++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/algorithm/sorter.go b/algorithm/sorter.go
index 8205a84..eafe118 100644
--- a/algorithm/sorter.go
+++ b/algorithm/sorter.go
@@ -10,7 +10,8 @@ import "github.com/duke-git/lancet/lancetconstraints"
 func BubbleSort[T any](slice []T, comparator lancetconstraints.Comparator) []T {
 	for i := 0; i < len(slice); i++ {
 		for j := 0; j < len(slice)-1-i; j++ {
-			if comparator.Compare(slice[j], slice[j+1]) == 1 {
+			isCurrGreatThanNext := comparator.Compare(slice[j], slice[j+1]) == 1
+			if isCurrGreatThanNext {
 				swap(slice, j, j+1)
 			}
 		}
@@ -57,6 +58,30 @@ func SelectionSort[T any](slice []T, comparator lancetconstraints.Comparator) []
 	return slice
 }
 
+// ShellSort shell sort slice.
+func ShellSort[T any](slice []T, comparator lancetconstraints.Comparator) []T {
+	size := len(slice)
+	if size <= 1 {
+		return slice
+	}
+
+	gap := 1
+	for gap < size/3 {
+		gap = 3*gap + 1
+	}
+
+	for gap >= 1 {
+		for i := gap; i < size; i++ {
+			for j := i; j >= gap && comparator.Compare(slice[j], slice[j-gap]) == -1; j -= gap {
+				swap(slice, j, j-gap)
+			}
+		}
+		gap /= 3
+	}
+
+	return slice
+}
+
 // func QuickSort[T comparable](slice []T, low, high int) []T {
 // 	if low < high {
 // 		var p int
diff --git a/algorithm/sorter_test.go b/algorithm/sorter_test.go
index c6522d9..e508a43 100644
--- a/algorithm/sorter_test.go
+++ b/algorithm/sorter_test.go
@@ -110,3 +110,16 @@ func TestSelectionSort(t *testing.T) {
 
 	asssert.Equal(expected, actual)
 }
+
+func TestShellSort(t *testing.T) {
+	asssert := internal.NewAssert(t, "TestShellSort")
+
+	comparator := &peopleAageComparator{}
+	sortedPeopleByAge := ShellSort(peoples, comparator)
+	t.Log(sortedPeopleByAge)
+
+	expected := "[{d 8} {b 10} {c 17} {a 20} {e 28}]"
+	actual := fmt.Sprintf("%v", sortedPeopleByAge)
+
+	asssert.Equal(expected, actual)
+}