from ortools.constraint_solver import routing_enums_pb2 from ortools.constraint_solver import pywrapcp

def create_data_model(): data = {} # Set the number of vehicles data['num_vehicles'] = 4 # Set the number of cities data['num_cities'] = 5 # Define the distances between cities data['distances'] = [ [0, 1, 2, 3, 4], # Distance from city 0 to cities 0, 1, 2, 3, 4 [1, 0, 2, 3, 4], # Distance from city 1 to cities 0, 1, 2, 3, 4 [2, 2, 0, 3, 4], # Distance from city 2 to cities 0, 1, 2, 3, 4 [3, 3, 3, 0, 4], # Distance from city 3 to cities 0, 1, 2, 3, 4 [4, 4, 4, 4, 0], # Distance from city 4 to cities 0, 1, 2, 3, 4 ] # Define the mapping of cities to vehicles data['city_to_vehicle'] = [[0, 1], [0], [1, 2], [2], [3]] # City i is mapped to vehicles j

return data

def main(): # Create the data model data = create_data_model()

# Create the routing index manager
manager = pywrapcp.RoutingIndexManager(data['num_cities'], data['num_vehicles'], data['city_to_vehicle'])

# Create the routing model
routing = pywrapcp.RoutingModel(manager)

# Set the cost function (distance) between cities
def distance_callback(from_index, to_index):
    # Convert from routing variable Index to distance matrix NodeIndex
    from_node = manager.IndexToNode(from_index)
    to_node = manager.IndexToNode(to_index)
    return data['distances'][from_node][to_node]

transit_callback_index = routing.RegisterTransitCallback(distance_callback)
routing.SetArcCostEvaluatorOfAllVehicles(transit_callback_index)

# Set the search parameters
search_parameters = pywrapcp.DefaultRoutingSearchParameters()
search_parameters.first_solution_strategy = (
    routing_enums_pb2.FirstSolutionStrategy.PATH_CHEAPEST_ARC)

# Solve the problem
solution = routing.SolveWithParameters(search_parameters)

# Print the solution
if solution:
    for vehicle_id in range(data['num_vehicles']):
        index = routing.Start(vehicle_id)
        plan_output = 'Route for vehicle {}:\n'.format(vehicle_id)
        while not routing.IsEnd(index):
            plan_output += ' {} ->'.format(manager.IndexToNode(index))
            index = solution.Value(routing.NextVar(index))
        plan_output += ' {}\n'.format(manager.IndexToNode(index))
        print(plan_output)
else:
    print('No solution found !')

if name == 'main': main()