My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Add solution for 2023/20
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2023/day20.py
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2023/day20.py
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import fileinput
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from collections import defaultdict, Counter, deque
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from itertools import count
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from utils import mul
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# Parse problem input.
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broadcaster = []
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flip_flops = defaultdict(list)
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conjunctions = defaultdict(list)
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graph = defaultdict(list)
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for line in fileinput.input():
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line = line.strip()
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if line.startswith('broadcaster'):
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outputs = line.split(' -> ')[1]
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for out in outputs.split(', '):
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broadcaster.append(out)
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elif line.startswith('%'):
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mod, outputs = line.split(' -> ')
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mod = mod[1:]
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for out in outputs.split(', '):
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flip_flops[mod].append(out)
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graph[out].append(mod)
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elif line.startswith('&'):
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mod, outputs = line.split(' -> ')
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mod = mod[1:]
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for out in outputs.split(', '):
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conjunctions[mod].append(out)
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graph[out].append(mod)
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def press_button(state):
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# Start the cycle with the broadcaster receiving a
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# low pulse from the button.
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horizon = deque([('broadcaster', False, 'button')])
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while horizon:
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dst, pulse, frm = horizon.popleft()
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# Output all pulses to be examined.
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yield dst, pulse
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if dst == 'broadcaster':
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for r in broadcaster:
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horizon.append((r, pulse, dst))
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elif dst in flip_flops:
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# If a flip-flop receives a high pulse, do nothing.
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if pulse is True:
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continue
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# Invert the state of the flip-flop.
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STATE[dst] = not STATE[dst]
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# Broadcast the new state to all output modules.
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for r in flip_flops[dst]:
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horizon.append((r, STATE[dst], dst))
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elif dst in conjunctions:
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# Set memory of this pulse.
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STATE[dst][frm] = pulse
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# If memory is all high pulses...
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for inp, mem in STATE[dst].items():
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if not mem:
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break
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else:
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# ...send a low pulse to all output modules.
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for r in conjunctions[dst]:
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horizon.append((r, False, dst))
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continue
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# Otherwise, send a high pulse to all output modules.
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for r in conjunctions[dst]:
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horizon.append((r, True, dst))
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# Solve problem.
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STATE = {k: False for k in flip_flops}
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for mod in conjunctions:
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STATE[mod] = {inp: False for inp in graph[mod]}
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# Need to find the aligned cycle of the four modules that
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# feed into conjunction X, where X feeds into `rx`.
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key_regs = graph[graph['rx'][0]]
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cycle_lens = {mod: -1 for mod in key_regs}
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pulse_counts = Counter()
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for cycle in count(start=1):
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for module, pulse in press_button(STATE):
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if pulse is False and cycle_lens.get(module) == -1:
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cycle_lens[module] = cycle
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if cycle <= 1000:
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pulse_counts[pulse] += 1
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if all(v != -1 for v in cycle_lens.values()):
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break
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print("Part 1:", mul(pulse_counts.values()))
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print("Part 2:", mul(cycle_lens.values()))