aoc/2023/14/solution.py

#!/usr/bin/python3
import sys

def pattern_str(pattern):
    return '\n'.join(map(''.join, pattern))

def rotate(pattern):
    return list(map(list, zip(*reversed(pattern))))

def shift(pattern):
    shifted = True
    while shifted:
        shifted = False
        for y in range(len(pattern)):
            for x in range(len(pattern[y]) - 1, 0, -1):
                if pattern[y][x] == '.' and pattern[y][x - 1] == 'O':
                    pattern[y][x], pattern[y][x - 1] = pattern[y][x - 1], pattern[y][x]
                    shifted = True
    return pattern

def part1():
    print('part 1')

    pattern = list(map(list, map(str.strip, sys.stdin.readlines())))
    print(f'pattern:\n{pattern_str(pattern)}')

    rotated = rotate(pattern)
    print(f'rotated:\n{pattern_str(rotated)}')

    shift(rotated)
    back = rotate(rotated)
    print(f'shifted:\n{pattern_str(back)}')

    total = 0
    for i, row in enumerate(back):
        total += sum([i + 1 for c in row if c == 'O'])
    print(f'total is {total}')

def pattern_hash(pattern):
    #return sum([sum([ord(pattern[k][l]) * l * k for l in range(len(pattern[k]))]) for k in range(len(pattern))])
    return hash(tuple(([hash(tuple(row)) for row in pattern])))

def part2():
    print('part 2')

    pattern = list(map(list, map(str.strip, sys.stdin.readlines())))
    #print(f'pattern:\n{pattern_str(pattern)}')

    cache = {}
    #patterns = {}
    for i in range(1000000000):
        for j in range(4):
            pattern = shift(rotate(pattern))
        hashed = pattern_hash(pattern)
        #print(f'cycle {i}: hash {hashed}')
        if hashed not in cache:
            cache[hashed] = i
            #patterns[hashed] = pattern
        else:
            break

    i += 1
    cache[hashed] += 1
    print(f'found repetition @{i} with hash {hashed} (previously occured @{cache[hashed]})')
    remaining = (1000000000 - cache[hashed]) % (i - cache[hashed])
    print(f'{remaining} cycles remaining')

    #print(f'first\n{pattern_str(patterns[hashed])}')
    #print(f'second\n{pattern_str(pattern)}')

    for i in range(remaining):
        for j in range(4):
            pattern = shift(rotate(pattern))

    total = 0
    # rotate upside down to compute easily
    pattern = rotate(rotate(pattern))
    for i, row in enumerate(pattern):
        total += sum([i + 1 for c in row if c == 'O'])
    print(f'total is {total}')

if sys.argv[1] in '1':
    part1()
else:
    part2()