fix: The LastIndexOf method can never return the index of the first element (#83)

Co-authored-by: JiangCheng <jiangcheng@kezaihui.com>

slice/slice.go

@@ -1094,7 +1094,7 @@ func IndexOf[T comparable](arr []T, val T) int {
 // LastIndexOf returns the index at which the last occurrence of the item is found in a slice or return -1 if the then cannot be found.
 // Play: https://go.dev/play/p/DokM4cf1IKH
 func LastIndexOf[T comparable](slice []T, item T) int {
-	for i := len(slice) - 1; i > 0; i-- {
+	for i := len(slice) - 1; i >= 0; i-- {
 		if item == slice[i] {
 			return i
 		}

slice/slice_test.go

@@ -665,8 +665,8 @@ func TestDifferenceWith(t *testing.T) {
 func TestDifferenceBy(t *testing.T) {
 	assert := internal.NewAssert(t, "TestDifferenceBy")
 
-	s1 := []int{1, 2, 3, 4, 5} //after add one: 2 3 4 5 6
+	s1 := []int{1, 2, 3, 4, 5} // after add one: 2 3 4 5 6
-	s2 := []int{3, 4, 5}       //after add one: 4 5 6
+	s2 := []int{3, 4, 5}       // after add one: 4 5 6
 	addOne := func(i int, v int) int {
 		return v + 1
 	}
@@ -873,8 +873,9 @@ func TestIndexOf(t *testing.T) {
 func TestLastIndexOf(t *testing.T) {
 	assert := internal.NewAssert(t, "TestLastIndexOf")
 
-	arr := []string{"a", "a", "b", "c"}
+	arr := []string{"a", "b", "b", "c"}
-	assert.Equal(1, LastIndexOf(arr, "a"))
+	assert.Equal(0, LastIndexOf(arr, "a"))
+	assert.Equal(2, LastIndexOf(arr, "b"))
 	assert.Equal(-1, LastIndexOf(arr, "d"))
 }