53 lines
1.4 KiB
Python
53 lines
1.4 KiB
Python
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from math import gcd
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def get_input(sample = False):
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with open("sample" if sample else 'input', 'r') as f:
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ret = []
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lines = f.readlines()
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ret.append(int(lines[0]))
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ret.append([int(x) if x != "x" else x for x in lines[1].split(',')])
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return ret
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def get_next_bus_departure(bus_id: int, cur_time: int):
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return bus_id * math.ceil(cur_time / bus_id)
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def get_result(data: list, part = 1):
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cur_time = data[0]
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busses = data[1]
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if part == 1:
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eta_n_bus = {}
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for bus in busses:
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if bus == 'x': continue
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eta = get_next_bus_departure(bus, cur_time)
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eta_n_bus[eta] = bus
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earliest = min(eta_n_bus.keys())
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earliest_bus = eta_n_bus[earliest]
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waiting_time = earliest - cur_time
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return waiting_time * earliest_bus
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else:
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step = busses[0]
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bus_n_offsets = [(bus, offset) for offset, bus in enumerate(busses) if bus != 'x']
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time = 0
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for bus, offset in bus_n_offsets[1:]:
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while True:
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time += step
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if (time + offset) % bus == 0:
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step = lcm(step, bus)
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break
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return time
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def lcm(a, b):
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return abs(a*b) // gcd(a, b)
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if __name__ == "__main__":
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print(get_result(get_input(), part = 2))
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