Advent of Code 2021 | Day 3 | Solution in Python3

December 3, 2021

Advent of Code 2021

Tanishq Chaudhary

I explore the solutions for the Advent of Code 2021 in Python3, for both the parts. Problem Link.

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Part 1 Solution

def get_input():
    data = []
    with open("input.txt") as f:
        data = f.readlines()
    return data

def solve(data):
    gamma, epsilon = "", ""
    for i in range(12):
        if sum(bits[i] == "1" for bits in data) > len(data)//2:
            gamma += "1"
            epsilon += "0"
        else:
            gamma += "0"
            epsilon += "1"
    return int(gamma, 2) * int(epsilon, 2)

print(solve(get_input()))

Part 2 Solution

from collections import Counter


def get_input():
    data = []
    with open("input.txt") as f:
        data = f.readlines()
    return data


def solve(data):
    data = get_input()
    i = 0
    while len(data) > 1:
        val = ""
        c = Counter([bits[i] for bits in data])
        val = "1" if c["1"] >= c["0"] else "0"
        data = [bits for bits in data if bits[i] == val]
        i += 1
    oxy = data[0]

    data = get_input()
    i = 0
    while len(data) > 1:
        val = ""
        c = Counter([bits[i] for bits in data])
        val = "0" if c["0"] <= c["1"] else "1"
        data = [bits for bits in data if bits[i] == val]
        i += 1
    co2 = data[0]

    return int(oxy, 2) * int(co2, 2)


print(solve(get_input()))

bits