Vehicle Routing with Pickups and Deliveries : Forcing all pickup before any delivery

[viethoangphp]

Hi everyone , I am having an issue with routing. I am using Google OR Tools for VRP (Vehicle Routing Problem) with Pickups and Deliveries. I want to ensure that, within a route, I must visit pickup points before making deliveries. How can I constrain this issue? .
For example, I have PickupsDeliveries = [[1,2], [3,4]]. After running the solution, the obtained result is 0 -> 3 -> 4 -> 1 -> 2. This is not the desired outcome. What I want is 0 -> 3 -> 1 -> 2 -> 4. That means visiting all pickup points before making deliveries.