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from typing import Generator
from collections.abc import Iterable
from collections import Counter
Bits = tuple[bool, ...]
Input = list[Bits]
def column(rows: Iterable[Bits], n: int) -> Generator[bool, None, None]:
for row in rows:
yield row[n]
def most_common(bits: Iterable[bool]) -> bool:
freqs: list[tuple[bool, int]] = Counter(bits).most_common()
if len(freqs) > 1 and freqs[0][1] == freqs[1][1]:
return True
return freqs[0][0]
def bits_to_int(bits: Bits) -> int:
ret: int = 0
for i, b in enumerate(reversed(bits)):
if b:
ret += 2 ** i
return ret
def part1(nums: Input) -> int:
nbits: int = len(nums[0])
gamma: Bits = tuple(most_common(column(inp, i)) for i in range(nbits))
epsilon: Bits = tuple(not bit for bit in gamma)
return bits_to_int(gamma) * bits_to_int(epsilon)
def part2_impl(nums: Input, complement: bool, bit: int = 0) -> Bits:
if len(nums) == 1:
return nums[0]
target: bool = most_common(column(nums, bit))
if complement:
target = not target
nums = list(filter(lambda n: n[bit] == target, nums))
return part2_impl(nums, complement, bit + 1)
def part2(nums: Input) -> int:
oxygen: Bits = part2_impl(nums, False)
co2: Bits = part2_impl(nums, True)
return bits_to_int(oxygen) * bits_to_int(co2)
inp: Input = [tuple(bool(int(c)) for c in l.strip()) for l in open('3.in')]
print(part1(inp))
print(part2(inp))
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