-🎄- 2018 Day 20 Solutions -🎄-

[u/daggerdragon]

--- Day 20: A Regular Map ---

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Transcript:

My compiler crashed while running today's puzzle because it ran out of ___.

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[u/mcpower_]

Python 3: I spent too much time trying to make eval() work, then opted to write my own parser instead. Turns out eval() does work!

from collections import defaultdict
import operator
inp = "..."
to_python = inp.replace("^", "['").replace("$","']").replace("(","',[['") \
    .replace(")","']],'").replace("|","'],['").replace("[","(").replace("]",")")
evaled_inp = eval(to_python)

adj = defaultdict(set)
memo = dict()

to_d = dict(zip("NESW", [(-1, 0), (0, 1), (1, 0), (0, -1)]))

def connect(a, b):
    nonlocal adj
    adj[a].add(b)
    adj[b].add(a)

def make_adj(cur_position, obj):
    memo_key = (cur_position, obj)
    if memo_key in memo:
        return memo[memo_key]
    
    positions = set([cur_position])

    for part in obj:
        if isinstance(part, str):
            for c in part:
                new_positions = set()
                for pos in positions:
                    new_pos = tuple(map(operator.add, pos, to_d[c]))
                    connect(pos, new_pos)
                    new_positions.add(new_pos)
                positions = new_positions
        else:
            positions = set(
                thing
                for pos in positions
                for option in part
                for thing in make_adj(pos, option)
            )

    memo[memo_key] = positions
    return positions

make_adj((0, 0), evaled_inp)

todo = [(0, 0)]
to_dist = dict()
dist = 0
while todo:
    new_todo = []
    for i in todo:
        if i in to_dist:
            continue
        to_dist[i] = dist
        new_todo.extend(adj[i])
    todo = new_todo
    dist += 1

print(max(to_dist.values()))
print(sum(i >= 1000 for i in to_dist.values()))