From 1fe4cdc429664de10904ab3b8b2fcf64e38a6664 Mon Sep 17 00:00:00 2001
From: dudaodong <lanliddd.2007@163.com>
Date: Mon, 6 Feb 2023 10:55:42 +0800
Subject: [PATCH] feat: add Difference and SymmetricDifference for list

---
 datastructure/list/list.go      | 40 ++++++++++++++++++++++++++++++++-
 datastructure/list/list_test.go | 22 ++++++++++++++++++
 2 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/datastructure/list/list.go b/datastructure/list/list.go
index ef77b0f..cea36e0 100644
--- a/datastructure/list/list.go
+++ b/datastructure/list/list.go
@@ -5,8 +5,9 @@
 package datastructure
 
 import (
-	"github.com/duke-git/lancet/v2/iterator"
 	"reflect"
+
+	"github.com/duke-git/lancet/v2/iterator"
 )
 
 // List is a linear table, implemented with slice.
@@ -317,6 +318,43 @@ func (l *List[T]) Intersection(other *List[T]) *List[T] {
 	return result
 }
 
+// Difference returns the difference between two collections.
+// return a list whose element in the original list, not in the given list.
+func (l *List[T]) Difference(other *List[T]) *List[T] {
+	result := NewList(make([]T, 0))
+
+	intersectList := l.Intersection(other)
+
+	for _, v := range l.data {
+		if !intersectList.Contain(v) {
+			result.data = append(result.data, v)
+		}
+	}
+
+	return result
+}
+
+// SymmetricDifference oppoiste operation of intersection function.
+func (l *List[T]) SymmetricDifference(other *List[T]) *List[T] {
+	result := NewList(make([]T, 0))
+
+	intersectList := l.Intersection(other)
+
+	for _, v := range l.data {
+		if !intersectList.Contain(v) {
+			result.data = append(result.data, v)
+		}
+	}
+
+	for _, v := range other.data {
+		if !intersectList.Contain(v) {
+			result.data = append(result.data, v)
+		}
+	}
+
+	return result
+}
+
 // SubList returns a sub list of the original list between the specified fromIndex, inclusive, and toIndex, exclusive.
 func (l *List[T]) SubList(fromIndex, toIndex int) *List[T] {
 	data := l.data[fromIndex:toIndex]
diff --git a/datastructure/list/list_test.go b/datastructure/list/list_test.go
index 0ce58ba..67a4319 100644
--- a/datastructure/list/list_test.go
+++ b/datastructure/list/list_test.go
@@ -328,6 +328,28 @@ func TestIntersection(t *testing.T) {
 	assert.Equal(true, expected.Equal(list3))
 }
 
+func TestDifference(t *testing.T) {
+	assert := internal.NewAssert(t, "TestDifference")
+
+	list1 := NewList([]int{1, 2, 3})
+	list2 := NewList([]int{1, 2, 4})
+	expected := NewList([]int{3})
+
+	list3 := list1.Difference(list2)
+	assert.Equal(true, expected.Equal(list3))
+}
+
+func TestSymmetricDifference(t *testing.T) {
+	assert := internal.NewAssert(t, "TestSymmetricDifference")
+
+	list1 := NewList([]int{1, 2, 3})
+	list2 := NewList([]int{1, 2, 4})
+	expected := NewList([]int{3, 4})
+
+	list3 := list1.SymmetricDifference(list2)
+	assert.Equal(true, expected.Equal(list3))
+}
+
 func TestSubSlice(t *testing.T) {
 	assert := internal.NewAssert(t, "TestSubSlice")