Fast Python solution for Day19 - one dimension at a time

day19.py

import itertools
from collections import Counter

lines = open("input/day19.txt").read().splitlines()
scanners = []
cur = None
for l in lines:
    if l == "":
        continue
    elif l[0:3] == "---":
        cur = []
        scanners.append(cur)
    else:
        cur.append(tuple(map(int, l.split(","))))

def try_align(aligned, candidate):
    ret = []
    dl = []
    dp = dpp = None
    for dim in range(3):
        x = [pos[dim] for pos in aligned]
        for (d,s) in [(0,1),(1,1),(2,1),(0,-1),(1,-1),(2,-1)]:
            if d == dp or d == dpp:
                continue
            t = [pos[d]*s for pos in candidate]
            w = [b-a for (a,b) in itertools.product(x, t)]
            c = Counter(w).most_common(1)
            if c[0][1] >= 12:
                break        
        if c[0][1] < 12:
            return None
        (dpp, dp) = (dp, d)
        ret.append([v - c[0][0] for v in t])
        dl.append(c[0][0])
    return (list(zip(ret[0],ret[1],ret[2])), dl)

done = set()
next = [ scanners[0] ]
rest = scanners[1:]
shifts = [(0,0,0)]
while next:
    aligned = next.pop()
    tmp = []
    for candidate in rest:
        r = try_align(aligned, candidate)
        if r:
            (updated, shift) = r
            shifts.append(shift)
            next.append(updated)
        else:
            tmp.append(candidate)
    rest = tmp
    done.update(aligned)

print(len(done))
sxs = itertools.product(shifts,shifts)
print(max(sum(abs(a-b) for (a,b) in zip(l,r)) for l,r in sxs))