#!/usr/bin/env python3 import sys from itertools import combinations, islice from intcode import read_program, run, run_inputs def read_grid(program): output = ''.join(map(chr, run(program))) lines = output.rstrip().split('\n') def gen_lines(): yield '.' * len(lines[0]) yield from lines yield '.' * len(lines[0]) return [list('.%s.' % line) for line in gen_lines()] def intersections(grid): for y, row in islice(enumerate(grid), 1, len(grid) - 1): for x, cell in islice(enumerate(row), 1, len(row) - 1): if row[x - 1:x + 2] == list('###') and \ grid[y - 1][x] == '#' and grid[y + 1][x] == '#': yield x, y def calibrate(grid): return sum((x - 1) * (y - 1) for x, y in intersections(grid)) def find_path(grid): x, y = next((x, y) for y, row in enumerate(grid) for x, cell in enumerate(row) if cell in '^v<>') dx, dy = {'^': (0, -1), 'v': (0, 1), '<': (-1, 0), '>': (1, 0)}[grid[y][x]] turn = None while True: # walk forward forward = 0 while grid[y + dy][x + dx] == '#': x += dx y += dy forward += 1 if forward > 0: # when blocked, turn right if turn: yield turn yield str(forward) turn = 'R' dx, dy = -dy, dx elif turn == 'R': # if right is blocked, turn left instead turn = 'L' dx, dy = -dx, -dy elif turn is None: turn = 'R' dx, dy = -dy, dx else: # if left is blocked too, we're at the end break def subroutines(path): for l in range(11, 1, -1): for i in range(len(path) - 2 * l): subseq = path[i:i + l] starts = [i] for j in range(i + l, len(path)): if path[j:j + l] == subseq: starts.append(j) if len(starts) > 1: yield l, starts def pick_subroutines(path): work = set() for l, starts in subroutines(path): for use in range(len(starts), 1, -1): for used_starts in combinations(starts, use): prio = -l * len(used_starts), -l work.add((prio, l, used_starts)) # get rid of overlaps taken = [False] * len(path) for prio, l, starts in sorted(work): if any(any(taken[i:i + l]) for i in starts): continue for start in starts: for i in range(start, start + l): taken[i] = True start = starts[0] yield ','.join(path[start:start + l]) def make_subroutines(path): path = list(path) subs = {'A': '', 'B': '', 'C': ''} main = ','.join(path) for name, sub in zip('ABC', islice(pick_subroutines(path), 3)): subs[name] = sub main = main.replace(sub, name) assert len(main) <= 20 assert all(len(sub) <= 20 for sub in subs.values()) return main, subs def rescue(program, main, subs): lines = [main, subs['A'], subs['B'], subs['C'], 'n'] inputs = map(ord, ('\n'.join(lines) + '\n')) for output in run_inputs(program, inputs): pass return output # part 1 program = read_program(sys.stdin) grid = read_grid(program) print(calibrate(grid)) # part 2 path = list(find_path(grid)) program[0] = 2 main, subs = make_subroutines(path) print(rescue(program, main, subs))