127 lines
4.4 KiB
Python
Executable File
127 lines
4.4 KiB
Python
Executable File
#!/usr/bin/env python3
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# Copyright 2010-2025 Google LLC
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# [START program]
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"""Simple Travelling Salesperson Problem (TSP) between cities."""
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# [START import]
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from ortools.constraint_solver import routing_enums_pb2
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from ortools.constraint_solver import pywrapcp
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# [END import]
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# [START data_model]
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def create_data_model():
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"""Stores the data for the problem."""
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data = {}
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data["distance_matrix"] = [
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[0, 2451, 713, 1018, 1631, 1374, 2408, 213, 2571, 875, 1420, 2145, 1972],
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[2451, 0, 1745, 1524, 831, 1240, 959, 2596, 403, 1589, 1374, 357, 579],
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[713, 1745, 0, 355, 920, 803, 1737, 851, 1858, 262, 940, 1453, 1260],
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[1018, 1524, 355, 0, 700, 862, 1395, 1123, 1584, 466, 1056, 1280, 987],
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[1631, 831, 920, 700, 0, 663, 1021, 1769, 949, 796, 879, 586, 371],
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[1374, 1240, 803, 862, 663, 0, 1681, 1551, 1765, 547, 225, 887, 999],
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[2408, 959, 1737, 1395, 1021, 1681, 0, 2493, 678, 1724, 1891, 1114, 701],
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[213, 2596, 851, 1123, 1769, 1551, 2493, 0, 2699, 1038, 1605, 2300, 2099],
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[2571, 403, 1858, 1584, 949, 1765, 678, 2699, 0, 1744, 1645, 653, 600],
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[875, 1589, 262, 466, 796, 547, 1724, 1038, 1744, 0, 679, 1272, 1162],
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[1420, 1374, 940, 1056, 879, 225, 1891, 1605, 1645, 679, 0, 1017, 1200],
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[2145, 357, 1453, 1280, 586, 887, 1114, 2300, 653, 1272, 1017, 0, 504],
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[1972, 579, 1260, 987, 371, 999, 701, 2099, 600, 1162, 1200, 504, 0],
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]
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data["num_vehicles"] = 1
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data["depot"] = 0
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return data
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# [END data_model]
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# [START solution_printer]
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def print_solution(manager, routing, solution):
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"""Prints solution on console."""
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print(f"Objective: {solution.ObjectiveValue()} miles")
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index = routing.Start(0)
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plan_output = "Route for vehicle 0:\n"
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route_distance = 0
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while not routing.IsEnd(index):
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plan_output += f" {manager.IndexToNode(index)} ->"
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previous_index = index
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index = solution.Value(routing.NextVar(index))
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route_distance += routing.GetArcCostForVehicle(previous_index, index, 0)
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plan_output += f" {manager.IndexToNode(index)}\n"
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plan_output += f"Route distance: {route_distance}miles\n"
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print(plan_output)
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# [END solution_printer]
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def main():
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"""Entry point of the program."""
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# Instantiate the data problem.
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# [START data]
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data = create_data_model()
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# [END data]
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# Create the routing index manager.
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# [START index_manager]
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manager = pywrapcp.RoutingIndexManager(
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len(data["distance_matrix"]), data["num_vehicles"], data["depot"]
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)
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# [END index_manager]
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# Create Routing Model.
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# [START routing_model]
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routing = pywrapcp.RoutingModel(manager)
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# [END routing_model]
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# [START transit_callback]
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def distance_callback(from_index, to_index):
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"""Returns the distance between the two nodes."""
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# Convert from routing variable Index to distance matrix NodeIndex.
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from_node = manager.IndexToNode(from_index)
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to_node = manager.IndexToNode(to_index)
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return data["distance_matrix"][from_node][to_node]
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transit_callback_index = routing.RegisterTransitCallback(distance_callback)
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# [END transit_callback]
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# Define cost of each arc.
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# [START arc_cost]
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routing.SetArcCostEvaluatorOfAllVehicles(transit_callback_index)
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# [END arc_cost]
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# Setting first solution heuristic.
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# [START parameters]
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search_parameters = pywrapcp.DefaultRoutingSearchParameters()
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search_parameters.first_solution_strategy = (
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routing_enums_pb2.FirstSolutionStrategy.PATH_CHEAPEST_ARC
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)
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# [END parameters]
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# Solve the problem.
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# [START solve]
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solution = routing.SolveWithParameters(search_parameters)
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# [END solve]
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# Print solution on console.
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# [START print_solution]
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if solution:
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print_solution(manager, routing, solution)
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# [END print_solution]
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if __name__ == "__main__":
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main()
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# [END program]
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