Table 1 Examples of natural and Gray labeling.

From: Efficient bit labeling in factorization machines with annealing for traveling salesman problem

Route

Natural

Gray

\(\textbf{r}\)

\(m(=\underline{m})\)

\(\underline{m}(\ne m)\)

\(\textbf{b} (= \underline{\textbf{b}})\)

\(\underline{\textbf{b}} (\ne \textbf{b})\)

\(|\mathcal {S}| (= |\underline{\mathcal {S}}|)\)

\(|\underline{\mathcal {S}}| (\ne |\mathcal {S}|)\)

\(\textbf{b} (= \underline{\textbf{b}})\)

\(\underline{\textbf{b}} (\ne \textbf{b})\)

(1,2,3,4)

0

24

00000

11000

(0,0,0)

(0,3,0)

00000

01000

(1,2,4,3)

1

25

00001

11001

(0,0,1)

(0,3,1)

00001

01001

(1,3,2,4)

2

26

00010

11010

(0,1,0)

–

00100

–

(1,3,4,2)

3

27

00011

11011

(0,1,1)

–

00101

–

(1,4,2,3)

4

28

00100

11100

(0,0,2)

(0,3,2)

00011

01011

(1,4,3,2)

5

29

00101

11101

(0,1,2)

–

00111

–

(2,1,3,4)

6

30

00110

11110

(1,0,0)

(1,3,0)

10000

11000

(2,1,4,3)

7

31

00111

11111

(1,0,1)

(1,3,1)

10001

11001

(2,3,1,4)

8

–

01000

–

(1,1,0)

–

10100

–

(2,3,4,1)

9

–

01001

–

(1,1,1)

–

10101

–

(2,4,1,3)

10

–

01010

–

(1,0,2)

(1,3,2)

10011

11011

(2,4,3,1)

11

–

01011

–

(1,1,2)

–

10111

–

(3,1,2,4)

12

–

01100

–

(0,2,0)

–

01100

–

(3,1,4,2)

13

–

01101

–

(0,2,1)

–

01101

–

(3,2,1,4)

14

–

01110

–

(1,2,0)

–

11100

–

(3,2,4,1)

15

–

01111

–

(1,2,1)

–

11101

–

(3,4,1,2)

16

–

10000

–

(0,2,2)

–

01111

–

(3,4,2,1)

17

–

10001

–

(1,2,2)

–

11111

–

(4,1,2,3)

18

–

10010

–

(0,0,3)

(0,3,3)

00010

01010

(4,1,3,2)

19

–

10011

–

(0,1,3)

–

00110

–

(4,2,1,3)

20

–

10100

–

(1,0,3)

(1,3,3)

10010

11010

(4,2,3,1)

21

–

10101

–

(1,1,3)

–

10110

–

(4,3,1,2)

22

–

10110

–

(0,2,3)

–

01110

–

(4,3,2,1)

23

–

10111

–

(1,2,3)

–

11110

–

  1. The forward labeling performs \(\textbf{r}\rightarrow \textbf{b}\), and the inverse one does \(\mathbf {\underline{b}}\rightarrow \textbf{r}\). Each set of \(\mathbf {\underline{m}}\), \(\mathbf {\underline{b}}\), and \(|\mathcal {\underline{S}}|\) is a superset of m, \(\textbf{b}\), and \(|\mathcal {S}|\), respectively. Only the extended eight elements are shown in the 3-rd, 5-th, 7-th, and 9-th columns.