Solutions to AoC 2021

advent_of_code_2021.py

import re
from itertools import permutations, combinations, count, chain, product
from typing import Dict, Tuple, Set, List, Iterator, Optional, Union
from collections import defaultdict
from functools import lru_cache
from math import prod

#### FILE INPUT AND PARSING ######################################
# Adapted from Peter Norvigs Advent of Code solutions, https://github.com/norvig/pytudes.
def Input(day, parser=str.split, sep='\n') -> list:
    "For this day's input file, return a list of sections separated by |sep| ad parsed by |parser|."
    if isinstance(day, int):
        sections = open(f'advent2021/input{day}.txt').read().rstrip('\n').split(sep)
        return [parser(section) for section in sections]
    return [parser(section) for section in day.rstrip('\n').split(sep)]

def do(day, *answers) -> List[int]:
    "E.g., do(3) returns [day3_1(in3), day3_2(in3)]. Verifies `answers` if given."
    g = globals()
    got = []
    for part in (1, 2):
        fname = f'day{day}_{part}'
        if fname in g: 
            got.append(g[fname](g[f'in{day}']))
            if len(answers) >= part: 
                assert got[-1] == answers[part - 1], (
                    f'{fname}(in{day}) got {got[-1]}; expected {answers[part - 1]}')
    return got
#################################################################

# Day 1: Sonar Sweep
# 1. Count number of numbers larger than the previous
# 2. Count number of sum of windows larger than previous sums
in1 : List[int] = Input(1, int)

def day1_1(nums):
    return sum(1 for x, y in zip(nums, nums[1:]) if y > x)

def day1_2(nums):
    sums = [sum(win) for win in zip(nums, nums[1:], nums[2:])]
    return sum(1 for x, y in zip(sums, sums[1:]) if y > x)

do(1, 1754, 1789)

# Day 2: Dive!
# 1. Calculate position from movement instructions
# 2. Use aim when calculating the position

Instruction = Tuple[str, int]

def parse_instr(line) -> Instruction:
    dir, val = line.split(' ')
    return dir, int(val)

in2 : List[Instruction] = Input(2, parse_instr)

def day2_1(instructions):
    pos, depth = 0, 0
    for dir, val in instructions:
        if dir == 'forward':
            pos += val
        elif dir == 'down':
            depth += val
        elif dir == 'up':
            depth -= val
    return pos * depth
            
def day2_2(instructions):
    pos, depth, aim = 0, 0, 0
    for dir, val in instructions:
        if dir == 'forward':
            pos += val
            depth += aim * val
        elif dir == 'down':
            aim += val
        elif dir == 'up':
            aim -= val
    return pos * depth

do(2, 1524750,1592426537)