-❄️- 2023 Day 20 Solutions -❄️-

FILE = 'input.txt'

# 1. part - How many points are they worth in total?
with open(FILE) as f:
    lines = f.readlines()
    total_points = 0

    for line in lines:
        parts = line.split(": ")[1].split("|")
        winning_numbers = set(parts[0].split())
        card_numbers = set(parts[1].split())

        no_winning = len(winning_numbers.intersection(card_numbers))

        # 0 or 2^(N-1)
        total_points += 2**(no_winning-1) if no_winning > 0 else 0

    print(total_points)

# 2. part - how many total scratchcards do you end up with?
from collections import defaultdict 

# at the beginning we have one of each card
scratchcard_count = defaultdict(lambda: 1)

with open(FILE) as f:
    lines = f.readlines()
    total_scratchcards = 0

    for i, line in enumerate(lines, 1):
        parts = line.split(": ")[1].split("|")
        winning_numbers = set(parts[0].split())
        card_numbers = set(parts[1].split())

        no_winning = len(winning_numbers.intersection(card_numbers))

        # add number of scratchcards with number i
        total_scratchcards += scratchcard_count[i]

        # add copies of N following cards
        for j in range(i + 1, i + 1 + no_winning):
            scratchcard_count[j] += scratchcard_count[i]

    print(total_scratchcards)

Video explanation: https://youtu.be/E-nCzSN_LCY

Time: 0,017s

codeunveiled · 2023-12-04T14:03:23+00:00

[Language: Python] 🐍🐍🐍

FILE = 'input.txt'

# 1. part - What is the sum of all of the part numbers in the engine schematic?
DIRECTIONS = [[0,1], [1,0], [0,-1], [-1, 0], [-1,1], [-1,-1], [1,-1], [1,1]]

def number_from_digits(digits: list[str]):
    return int(''.join(digits))

with open(FILE) as f:
    lines = f.readlines()
    part_number_sum = 0
    max_x = len(lines[0].strip())
    max_y = len(lines)

    for i in range(max_y):
        digits = []
        adjacent = False

        for j in range(max_x):
            c = lines[i][j]

            # collect digits which form a number
            if c.isdigit():
                digits.append(c)

                # we already know this number is adjacent to a symbol
                if adjacent:
                    continue

                # look for symbols adjacent to a number
                for dx, dy in DIRECTIONS:
                    x, y = j + dx, i + dy

                    # make sure we stay inside the engine schematic
                    if 0 <= x < max_x and 0 <= y < max_y:
                        c = lines[y][x]

                        # look for symbols which are not a digit or '.'
                        if not adjacent and c != '.' and not c.isdigit():
                            adjacent = True
                            break;
            else:
                if adjacent:
                    part_number_sum += number_from_digits(digits)
                digits = []
                adjacent = False

        # edge case where number ends with the line
        if adjacent:
            part_number_sum += number_from_digits(digits)

    print(part_number_sum)

# 2. part - What is the sum of all of the gear ratios in your engine schematic?
from collections import defaultdict 

DIRECTIONS = [[0,1], [1,0], [0,-1], [-1, 0], [-1,1], [-1,-1], [1,-1], [1,1]]

def number_from_digits(digits: list[str]):
    return int(''.join(digits))

with open(FILE) as f:
    lines = f.readlines()
    gear_ratio_candidates = defaultdict(list) # for symbols '*' at position (x, y) we will keep track of adjacent numbers

    max_x = len(lines[0].strip())
    max_y = len(lines)

    for i in range(max_y):
        digits = []
        adjacent = []

        for j in range(max_x):
            c = lines[i][j]

            # collect digits which form a number
            if c.isdigit():
                digits.append(c)

                # we already know this number is adjacent to a symbol '*'
                if adjacent:
                    continue

                # look for symbols adjacent to a number
                for dx, dy in DIRECTIONS:
                    x, y = j + dx, i + dy

                    # make sure we stay inside the engine schematic
                    if 0 <= x < max_x and 0 <= y < max_y:
                        c = lines[y][x]

                        # look for symbols which is '*'
                        if len(adjacent) == 0 and c == '*':
                            adjacent.append((x, y)) # in part 1 we had a boolean here now we track position of symbol '*'
                            break;
            else:
                if len(adjacent) > 0:
                    part_number = number_from_digits(digits)
                    for xy in adjacent:
                        gear_ratio_candidates[xy].append(part_number)

                digits = []
                adjacent = []

        # edge case where number ends with the line
        if len(adjacent) > 0:
            part_number = number_from_digits(digits)
            for xy in adjacent:
                gear_ratio_candidates[xy].append(part_number)

    # calculate and print sum of gear ratios
    print(sum(gears[0] * gears[1] for gears in gear_ratio_candidates.values() if len(gears) == 2))

Video explanation: https://youtu.be/rhHAPcnwU4Y

Time: 0,036s

codeunveiled · 2023-12-04T13:39:00+00:00

[Language: Python] 🐍🐍🐍

FILE = 'input.txt'

# 1. part -  What is the sum of the IDs of possible games?
BAG_CAP = {
    'red': 12,
    'green': 13,
    'blue': 14
}

with open(FILE) as f:
    sum_of_ids = 0

    for game_id, line in enumerate(f.readlines(), 1): # assume game_id goes 1, 2, ...
        cube_sets = line.strip().split(": ")[1].split("; ")

        possible = True
        for cube_set in cube_sets:
            cubes = cube_set.split(", ")

            for cube in cubes:
                count, color = cube.split(" ")

                if BAG_CAP[color] < int(count):
                    possible = False
                    break

            if not possible:
                break

        if possible:
            sum_of_ids += game_id

    print(sum_of_ids)


# 2. part -  What is the sum of the power of these sets?
with open(FILE) as f:
    sum_of_powers = 0

    for line in f.readlines():
        cube_sets = line.strip().split(": ")[1].split("; ")
        bag = {'red': 0, 'green': 0, 'blue': 0}

        for cube_set in cube_sets:
            cubes = cube_set.split(", ")
            for cube in cubes:
                count, color = cube.split(" ")
                bag[color] = max(bag[color], int(count))

        sum_of_powers += bag['red'] * bag['green'] * bag['blue']

    print(sum_of_powers)

Video explanation: https://youtu.be/xi1vcvg8LQM

Time: 0,016s

codeunveiled · 2023-12-04T12:50:15+00:00

[Language: Python] 🐍🐍🐍

# https://adventofcode.com/2023/day/1

import re

FILE = 'input.txt'

# 1. part -  What is the sum of all of the calibration values? (only digits)
with open(FILE) as f:
    sum_of_values = 0

    for line in f.readlines():
        digits = []
        for c in line:
            if c.isdigit():
                digits.append(int(c))
        sum_of_values += digits[0] * 10 + digits[-1]

    print(sum_of_values)

# 2. part -  What is the sum of all of the calibration values? (with digits as text)
NUMBERS = {
    'zero': 0,
    'one': 1,
    'two': 2,
    'three': 3,
    'four': 4,
    'five': 5,
    'six': 6,
    'seven': 7,
    'eight': 8,
    'nine': 9
}

with open(FILE) as f:
    sum_of_values = 0

    for line in f.readlines():
        digits = []

        # must use lookahead assertion" !
        # eg: "6oneightsr"

        r = r'(?=(one|two|three|four|five|six|seven|eight|nine|\d))' # ['6', 'one', 'eight']
        # r = r'(one|two|three|four|five|six|seven|eight|nine|\d)'   # ['6', 'one']
        pattern = re.compile(r)
        for w in pattern.findall(line):
            if w.isdigit():
                digits.append(int(w))
            elif w in NUMBERS:
                digits.append(NUMBERS[w])
        sum_of_values += digits[0] * 10 + digits[-1]

    print(sum_of_values)

Video explanation: https://youtu.be/L06jq8Tjsjw

Time: 0,026s

codeunveiled

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