133 lines
3.3 KiB
Python
Executable File
133 lines
3.3 KiB
Python
Executable File
#! /usr/bin/env python3
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import sys
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import math
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from typing import List
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from typing import Tuple
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def read_file(filename: str) -> Tuple[int, List[int]]:
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with open(filename) as f:
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ts = int(next(f).strip())
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busses = [
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int(bus) if bus != "x" else -1
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for bus in next(f).strip().split(",")
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]
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return ts, busses
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def read_cli(arg: str) -> List[int]:
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busses = [
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int(bus) if bus != "x" else -1
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for bus in arg.strip().split(",")
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]
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return busses
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def wait_time(ts: int, bus_id: int) -> int:
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return (bus_id - (ts % bus_id) % bus_id)
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def part1():
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ts, busses = read_file("input.txt")
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min_wait = -1
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min_bus_id = 0
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for bus_id in busses:
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if bus_id < 0:
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continue
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w = wait_time(ts, bus_id)
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if min_wait < 0 or w < min_wait:
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min_wait = w
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min_bus_id = bus_id
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print(f"Wait {min_wait} for bus {min_bus_id}. Answer {min_wait * min_bus_id}")
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def part2(busses=None, start=0):
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if busses is None:
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_, busses = read_file("input.txt")
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# busses = [7, 13, -1, -1, 59, -1, 31, 19]
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t = start
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# t = 100000000000000
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# t = t - (t%7)
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# if t%7 != 0:
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# print("Not starting with multiple of 7")
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# return
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while True:
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# print(f"Checking time {t}")
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for i, bus_id in enumerate(busses):
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if bus_id < 0:
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continue
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if i == 0:
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w = t % bus_id
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else:
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w = wait_time(t, bus_id)
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# print(f"Wait for bus {bus_id} is {w} expect {i}")
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if w != i:
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if i > 0:
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t += busses[0]
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else:
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t += 1
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break
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else:
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print(f"All busses match for time {t}")
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break
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def part2_calc(busses=None, start=0):
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if busses is None:
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_, busses = read_file("input.txt")
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# busses = [7, 13, -1, -1, 59, -1, 31, 19]
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t = start
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last_index = 0
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product = -1
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while True:
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print(f"Checking time {t}")
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for i, bus_id in enumerate(busses[last_index:], last_index):
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if bus_id < 0:
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continue
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if i == 0:
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w = t % bus_id
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else:
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w = wait_time(t, bus_id)
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print(f"Wait for bus {bus_id} is {w} expect {i}")
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if w == i % bus_id:
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last_index = i+1
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if product < 0:
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product = bus_id
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else:
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product = product * bus_id
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print(f"New index {last_index}, new product {product}")
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else:
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if i > 0:
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t += product
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else:
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t += 1
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break
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else:
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print(f"All busses match for time {t}")
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break
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if __name__ == "__main__":
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if len(sys.argv) == 1:
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part1()
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part2_calc()
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else:
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busses = read_cli(sys.argv[1])
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b1, b2 = busses[0], busses[1]
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t = b1 * math.floor(b2/b1)
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print(f"Maybe t = {t}")
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start = 0
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if len(sys.argv) > 2:
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start = int(sys.argv[2])
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print("brute")
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part2(busses, start)
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print("")
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print("calc")
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part2_calc(busses, start)
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