chore: added generic input for combinations (#12)

Co-authored-by: Max Schmitt <max@schmitt.mx>

combinations.go

@@ -5,13 +5,13 @@ import "math/bits"
 
 // All returns all combinations for a given string array.
 // This is essentially a powerset of the given set except that the empty set is disregarded.
-func All(set []string) (subsets [][]string) {
+func All[T any](set []T) (subsets [][]T) {
 	length := uint(len(set))
 
 	// Go through all possible combinations of objects
 	// from 1 (only first object in subset) to 2^length (all objects in subset)
 	for subsetBits := 1; subsetBits < (1 << length); subsetBits++ {
-		var subset []string
+		var subset []T
 
 		for object := uint(0); object < length; object++ {
 			// checks if object is contained in subset
@@ -29,7 +29,7 @@ func All(set []string) (subsets [][]string) {
 
 // Combinations returns combinations of n elements for a given string array.
 // For n < 1, it equals to All and returns all combinations.
-func Combinations(set []string, n int) (subsets [][]string) {
+func Combinations[T any](set []T, n int) (subsets [][]T) {
 	length := uint(len(set))
 
 	if n > len(set) {
@@ -43,7 +43,7 @@ func Combinations(set []string, n int) (subsets [][]string) {
 			continue
 		}
 
-		var subset []string
+		var subset []T
 
 		for object := uint(0); object < length; object++ {
 			// checks if object is contained in subset

combinations_test.go

@@ -78,6 +78,78 @@ func TestStringCombinations(t *testing.T) {
 	}
 }
 
+func TestIntegerCombinations(t *testing.T) {
+	tt := []struct {
+		name string
+		in   []int
+		out  [][]int
+	}{
+		{
+			name: "Empty slice",
+			in:   []int{},
+			out:  nil,
+		},
+		{
+			name: "Single item",
+			in:   []int{1},
+			out: [][]int{
+				{1},
+			},
+		},
+		{
+			name: "Two items",
+			in:   []int{1, 2},
+			out: [][]int{
+				{1},
+				{2},
+				{1, 2},
+			},
+		},
+		{
+			name: "Three items",
+			in:   []int{1, 2, 3},
+			out: [][]int{
+				{1},
+				{2},
+				{1, 2},
+				{3},
+				{1, 3},
+				{2, 3},
+				{1, 2, 3},
+			},
+		},
+		{
+			name: "Four items",
+			in:   []int{1, 2, 3, 4},
+			out: [][]int{
+				{1},
+				{2},
+				{1, 2},
+				{3},
+				{1, 3},
+				{2, 3},
+				{1, 2, 3},
+				{4},
+				{1, 4},
+				{2, 4},
+				{1, 2, 4},
+				{3, 4},
+				{1, 3, 4},
+				{2, 3, 4},
+				{1, 2, 3, 4},
+			},
+		},
+	}
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			out := All(tc.in)
+			if !reflect.DeepEqual(out, tc.out) {
+				t.Errorf("error: \nreturn:\t%v\nwant:\t%v", out, tc.out)
+			}
+		})
+	}
+}
+
 func ExampleAll() {
 	combinations := All([]string{"A", "B", "C"})
 	fmt.Println(combinations)