feat: add temporary beaultiful triplets problem

implementation/beautiful_triplets.go

@@ -0,0 +1,5 @@
+package implementation
+
+func beautifulTriplets(d int32, arr []int32) int32 {
+	return 0
+}

implementation/beautiful_triplets_test.go

@@ -0,0 +1,32 @@
+package implementation
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type beautifulTripletsTestCase struct {
+	d      int32
+	arr    []int32
+	result int32
+}
+
+func TestBeaultifulTriplets(t *testing.T) {
+	tests := []beautifulTripletsTestCase{
+		{
+			result: 3,
+			d:      3,
+			arr:    []int32{1, 2, 4, 5, 7, 8, 10},
+		},
+		{
+			result: 2,
+			d:      3,
+			arr:    []int32{1, 6, 7, 7, 8, 10, 12, 13, 14, 19},
+		},
+	}
+
+	for _, test := range tests {
+		assert.Equal(t, test.result, beautifulTriplets(test.d, test.arr))
+	}
+}