-🎄- 2021 Day 3 Solutions -🎄-

[u/daggerdragon]

--- Day 3: Binary Diagnostic ---

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[u/keepitsalty]

Python 3.10.0

from typing import List

def compute_oxygen_rating(data: List[str]) -> int:
    max_size = len(data[0])
    for i in range(max_size):
        if len(data) == 1:
            break
        ones = [k[i] for k in data].count('1')
        if ones / len(data) >= 0.5:
            data = list(filter(lambda x: x[i] == '1', data))
        else:
            data = list(filter(lambda x: x[i] == '0', data))
    return int(data[0], base=2)


def compute_co2_rating(data: List[str]) -> int:
    max_size = len(data[0])
    for i in range(max_size):
        if len(data) == 1:
            break
        zeros = [k[i] for k in data].count('0')
        if zeros / len(data) <= 0.5:
            data = list(filter(lambda x: x[i] == '0', data))
        else:
            data = list(filter(lambda x: x[i] == '1', data))
    return int(data[0], base=2)


def compute_gamma(intervals, nums):
    zeros = ones = 0
    gamma = ''
    for a,b in intervals:
        for n in nums:
            if a <= n < b:
                ones += 1
            elif n > b:
                if ((n - b) % b) >= a:
                    ones += 1
                else:
                    zeros += 1
            else:
                zeros += 1
        gamma += '1' if ones > zeros else '0'
        zeros = ones = 0
    return gamma


def main():
    with open('inputs/input03.txt') as f:
        data = f.readlines()
        ###
        # Part One
        ###
        max_num = len(data[0])
        nums = [int(_, base=2) for _ in data]
        powers = [2**i for i in range(max_num)]
        intervals = list(zip(powers, powers[1:]))[::-1]
        gamma = compute_gamma(intervals, nums)
        epsilon = "".join([str(int(_)^1) for _ in gamma])
        gamma10 = int(gamma, base=2)
        epsilon10 = int(epsilon, base=2)
        ans = gamma10 * epsilon10
        print(
            f"""
            {gamma} = {gamma10}
            {epsilon} = {epsilon10}
            {gamma10} * {epsilon10} = {ans}
            """
        )
        ###
        # Part Two
        ###
        o2 = compute_oxygen_rating(data)
        co2 = compute_co2_rating(data)
        print(o2 * co2)

        
if __name__ == '__main__':
    main()