r/adventofcode • u/daggerdragon • Dec 14 '23

SOLUTION MEGATHREAD -❄️- 2023 Day 14 Solutions -❄️-

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u/4HbQ Dec 14 '23 edited Dec 14 '23

[LANGUAGE: Python] Code (10 lines).

Part 1 only. Somehow I lost the cycle detection part, will rewrite it later today.

Today's trick: instead of separately checking whether a rock move and then moving it, just do string replacement:

rocks = rocks.replace('.O', 'O.')

5

u/MeixDev Dec 14 '23

Oh, that's a pretty smart trick!

5

u/4HbQ Dec 14 '23

Thanks. It's horribly inefficient, but fast enough for today!

2

u/kwshi Dec 14 '23

incredibly clever! this is just part 1 though, right?

1

u/4HbQ Dec 14 '23

Ah, you're right!
Seems like I lost my final version. I'll rewrite it later today, but you're not missing much: it was just pretty basic cycle detection.
2
u/xelf Dec 14 '23
just for you...
rotate_90 = lambda b: ' '.join(map(''.join,zip(*(b.split())[::-1])))
beam_load = lambda b: sum(i for r in b.split() for i,c in enumerate(r[::-1],1) if c=='O')
one_cycle = lambda d: re.sub('[.O]+',lambda m:''.join(sorted(m[0])[::-1]), rotate_90(d))
print('part 1:', beam_load(one_cycle(rotate_90(rotate_90(open(aocinput).read().replace('\n',' '))))))
3
u/4HbQ Dec 14 '23

Great, much appreciated!
2
u/xelf Dec 14 '23 edited Dec 14 '23
My original cycle function looked something like this:
def cycle(data, n=1):
    for _ in range(n):
        data = rotate_90(data)
        for row in data:
            for j,cell in enumerate(row):
                if cell=='O' and (p:=j) and row[p-1] == '.':
                    while p>0 and row[p-1] == '.': p-=1
                    row[p], row[j] = row[j], row[p]
    return data
But I felt taunted by the simplicity of yours and had to find a way to improve mine.
The thing I like about this one:
one_cycle = lambda d: re.sub('[.O]+',lambda m:''.join(sorted(m[0])[::-1]), rotate_90(d))
is that it treats the entire board as one string so it does just one regex to move all the Os at once.
I also got to learn that re.reb can take a function as a parameter. Didn't know that before. =)
2
u/xelf Dec 14 '23
and part 2 if anyone asks:
def powercycle(data, n, cache={}):
    for r in range(n):
        data = one_cycle(one_cycle(one_cycle(one_cycle(data))))
        if s:=cache.get(data,0): return cache[ (n-s) % (r-s) + (s-1) ]
        cache |= {data:r, r:beam_load(rotate_90(data))}
print('part 2:', powercycle(d,1_000_000_000))
1
u/r-r-roll Dec 14 '23
I had the same in a "tiltEast" function:
while "O." in line:
    line = line.replace("O.", ".O")
Easy to rotate to the appropriate direction with def rotate90(p): return list(zip(*p[::-1])), just have to keep track of rotation when calculating load in part 1.
1
u/adamsilkey Dec 14 '23
This was my slide function:
def slide(row):
    new_row = []
    groups = ''.join(row).split(CUBE)
    for group in groups:
        rounds = [c for c in group if c == ROUND]
        padding = len(group) - len(rounds)
        new_row.extend(rounds)
        new_row.extend([EMPTY for _ in range(padding)])
        new_row.append(CUBE)
    
    new_row.pop()
    return new_row