Sean McLemon | Advent of Code

2022-12-03 - Rucksack Reorganization

(original .ipynb)

Day 3 puzzle input is a list of ascii strings which represent a rucksacks with two compartments that contains some items (mine is here). Part 1 involves looking at each rucksack's contents, finding how many items occur in both compartments and summing the results for all rucksacks. Part 2 is taking groups of three rucksacks, finding how many items occur in any compartment in all three - then calculating the sum of these for all groups.

puzzle_input_str = open("./puzzle_input/day3.txt").read()

test_input_str = """vJrwpWtwJgWrhcsFMMfFFhFp
jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
PmmdzqPrVvPwwTWBwg
wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
ttgJtRGJQctTZtZT
CrZsJsPPZsGzwwsLwLmpwMDw"""


def get_priority(item):
    c = ord("A") if item.isupper() else ord("a")
    base = 27 if item.isupper() else 1
    return  ord(item) + base - c


def sum_items_both_compartments(comp1, comp2):
    s1, s2 = set(comp1), set(comp2)
    return sum(get_priority(i) for i in s1.intersection(s2))
    

def parse_rucksack(line):
    mid = int(len(line)/2)
    return line[:mid], line[mid:]


def part_one(input_str):
    return sum(
        sum_items_both_compartments(*parse_rucksack(line))
        for line
        in input_str.split("\n")
    )


assert 157 == part_one(test_input_str)

print("part one:", part_one(puzzle_input_str))

part one: 7821

def part_two(input_str):
    rucksacks = [set(line) for line in input_str.split("\n")]
    total = 0
    
    for i in list(range(0, len(rucksacks), 3)):
        badge = rucksacks[i].intersection(rucksacks[i+1]).intersection(rucksacks[i+2])
        total += get_priority(badge.pop())
        
    return total


assert 70 == part_two(test_input_str)

print("part two:", part_two(puzzle_input_str))

part two: 2752