Add moser-de bruijin sequence (#255)

Author: cp-sumi-k

math/moserdebruijnsequence/sequence.go

@@ -0,0 +1,34 @@
+// The Moser-de Bruijn sequence is the sequence obtained by
+// adding up the distinct powers of the number 4 (For example 1, 4, 16, 64, etc).
+// You can get more details on https://en.wikipedia.org/wiki/Moser%E2%80%93de_Bruijn_sequence.
+
+package moserdebruijnsequence
+
+func MoserDeBruijnSequence(number int) []int {
+	sequence := []int{}
+
+	for i := 0; i < number; i++ {
+		res := generateNthTerm(i)
+		sequence = append(sequence, res)
+	}
+
+	return sequence
+}
+
+func generateNthTerm(num int) int {
+	if num == 0 || num == 1 {
+		return num
+	}
+
+	//number is even
+	if num%2 == 0 {
+		return 4 * generateNthTerm(num/2)
+	}
+
+	//number is odd
+	if num%2 != 0 {
+		return 4*generateNthTerm(num/2) + 1
+	}
+
+	return 0
+}

math/moserdebruijnsequence/sequence_test.go

@@ -0,0 +1,25 @@
+package moserdebruijnsequence
+
+import (
+	"reflect"
+	"testing"
+)
+
+var testCases = []struct {
+	name     string
+	inputNum int
+	expected []int
+}{
+	{"first 15 terms", 15, []int{0, 1, 4, 5, 16, 17, 20, 21, 64, 65, 68, 69, 80, 81, 84}},
+}
+
+func TestMoserDeBruijnSequence(t *testing.T) {
+
+	for _, test := range testCases {
+		t.Run(test.name, func(t *testing.T) {
+			if output := MoserDeBruijnSequence(test.inputNum); !reflect.DeepEqual(output, test.expected) {
+				t.Errorf("For input: %d, expected: %v, but got: %v", test.inputNum, test.expected, output)
+			}
+		})
+	}
+}