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# tsp.py
# From Classic Computer Science Problems in Python Chapter 9
# Copyright 2018 David Kopec
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from typing import Dict, List, Iterable, Tuple
from itertools import permutations
vt_distances: Dict[str, Dict[str, int]] = {
"Rutland":
{"Burlington": 67,
"White River Junction": 46,
"Bennington": 55,
"Brattleboro": 75},
"Burlington":
{"Rutland": 67,
"White River Junction": 91,
"Bennington": 122,
"Brattleboro": 153},
"White River Junction":
{"Rutland": 46,
"Burlington": 91,
"Bennington": 98,
"Brattleboro": 65},
"Bennington":
{"Rutland": 55,
"Burlington": 122,
"White River Junction": 98,
"Brattleboro": 40},
"Brattleboro":
{"Rutland": 75,
"Burlington": 153,
"White River Junction": 65,
"Bennington": 40}
}
vt_cities: Iterable[str] = vt_distances.keys()
city_permutations: Iterable[Tuple[str, ...]] = permutations(vt_cities)
tsp_paths: List[Tuple[str, ...]] = [c + (c[0],) for c in city_permutations]
if __name__ == "__main__":
best_path: Tuple[str, ...]
min_distance: int = 99999999999 # arbitrarily high number
for path in tsp_paths:
distance: int = 0
last: str = path[0]
for next in path[1:]:
distance += vt_distances[last][next]
last = next
if distance < min_distance:
min_distance = distance
best_path = path
print(f"The shortest path is {best_path} in {min_distance} miles.")