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https://github.com/cupcakearmy/advent-of-code.git
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77 lines
2.1 KiB
Python
77 lines
2.1 KiB
Python
from os.path import join, dirname
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from typing import List, Tuple
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from math import ceil, floor
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class Station:
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def __init__(self, txt: str) -> None:
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arrival, busses = txt.strip().split('\n')
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self.arrival = int(arrival)
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self.busses = [
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int(bus)
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for bus in busses.replace('x', '0').split(',')
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]
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@staticmethod
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def get_next_for_id(id: int, arrival: int) -> int:
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return id * ceil(arrival / id)
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def find_next(self) -> Tuple[int, int]:
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arrivals: List[Tuple[int, int]] = []
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for bus in self.busses:
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if bus == 0:
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continue
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arrivals.append((bus, self.get_next_for_id(bus, self.arrival)))
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return min(arrivals, key=lambda x: x[1])
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def get_flag(self) -> int:
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id, arrives = self.find_next()
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return id * (arrives - self.arrival)
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def contest(self, offset: int = 1) -> int:
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# Prepare
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highest = max(self.busses)
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highest_i = self.busses.index(highest)
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others = [
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(bus, i - highest_i)
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for i, bus in enumerate(self.busses)
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if bus != 0 and i != highest_i
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]
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others.sort(key=lambda x: x[0], reverse=True)
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# Compute
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i: int = max(1, floor(offset / highest))
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while True:
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x = highest * i
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error = False
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for bus, diff in others:
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dx = x + diff
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if dx != self.get_next_for_id(bus, dx):
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error = True
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break
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if not error:
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return x - highest_i
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i += 1
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data = join(dirname(__file__), '../data.txt')
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with open(data) as f:
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# Some "testing"
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all = {
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'17,x,13,19': 3417,
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'67,7,59,61': 754018,
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'67,x,7,59,61': 779210,
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'67,7,x,59,61': 1261476,
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'1789,37,47,1889': 1202161486,
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}
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for busses, expected in all.items():
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station = Station('69\n' + busses)
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print(expected, expected == station.contest())
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txt = f.read()
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station = Station(txt)
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print(station.get_flag())
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print(station.contest(offset=10**14))
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