Algorithm 2: First neighborhood operator
Notations:
NSN	Number of demand nodes (Number of columns).
RAIN	A random integer number in the range of$[1,NSN]$.
NOR	Number of rows in a solution ($\mathit{nor}=1,2,\cdots ,NOR)$.
${\mathit{R}\mathit{N}\mathit{P}}_1$	First random position number.
${\mathit{R}\mathit{N}\mathit{P}}_2$	Second random position number (${\mathit{RNP}}_1\ne {\mathit{RNP}}_2)$.
${\mathit{N}\mathit{U}\mathit{C}}_{\mathit{n}\mathit{o}\mathit{r}}$	Number of used (non-empty) cells on the ${\mathit{nor}}^{\mathit{th}}$ row.
${\mathit{V}\mathit{A}\mathit{L}}_{\mathit{n}\mathit{o}\mathit{r}}^{{\mathit{R}\mathit{N}\mathit{P}}_1}$	The value on the ${\mathit{RNP}}_1$ column and $\mathit{nor}$ row.
${\mathit{V}\mathit{A}\mathit{L}}_{\mathit{n}\mathit{o}\mathit{r}}^{{\mathit{R}\mathit{N}\mathit{P}}_2}$	The value on the ${\mathit{RNP}}_2$ column and $\mathit{nor}$ row.
STR	A set to store random numbers.
1.	Generate an integer random number (RAIN) on the $[1,NSN]$;
2.	Preserve the first RAIN columns;
3.	For$\mathit{nor}=1$toNORdo
4.	Empty the set STR;
5.	Choose a random position (${\mathit{RNP}}_1)$ in the range $[RAIN+1,{\mathit{NUC}}_{\mathit{nor}}]$;
6.	Add ${\mathit{RNP}}_1$ to the set STR;
7.	Choose a random position (${\mathit{RNP}}_2)$ in the range $[RAIN+1,{\mathit{NUC}}_{\mathit{nor}}]$;
8.	If${\mathit{RNP}}_2\notin STR$do
9.	Swap the ${\mathit{VAL}}_{\mathit{nor}}^{{\mathit{RNP}}_1}$ and ${\mathit{VAL}}_{\mathit{nor}}^{{\mathit{RNP}}_2}$;
10.	End if
11.	End For
	Output: A new feasible solution.