Mathematical Problems in Engineering

Research Article

A Hybrid GRASP+VND Heuristic for the Two-Echelon Vehicle Routing Problem Arising in City Logistics

Algorithm 3

VND for the improvement of a solution .
( )   Define the neighborhood = Shift, Swap, Cross, …
( )     ;
( )   repeat
( )      improve_flag ←false;
( )      ;
( )      while     do
( )       ← LocalSearch( , );
( )      if  Cost( ) < Cost( )  then
( )         improve_flag ←true;
( )       ;
( )       ;
( )   end if
( )   end while
( ) until  improve_flag = false
( ) return the local optimum found;