import sys import numpy as np import parse def part1(sensor_to_beacon: dict[tuple[int, int], tuple[int, int]], row: int) -> int: no_beacons_row_l: list[np.ndarray] = [] for (sx, sy), (bx, by) in sensor_to_beacon.items(): d = abs(sx - bx) + abs(sy - by) # closest no_beacons_row_l.append(sx - np.arange(0, d - abs(sy - row) + 1)) no_beacons_row_l.append(sx + np.arange(0, d - abs(sy - row) + 1)) beacons_at_row = set(bx for (bx, by) in sensor_to_beacon.values() if by == row) no_beacons_row = set(np.concatenate(no_beacons_row_l)).difference(beacons_at_row) return len(no_beacons_row) def part2_intervals( sensor_to_beacon: dict[tuple[int, int], tuple[int, int]], xy_max: int ) -> tuple[int, int, int]: from tqdm import trange for y in trange(xy_max + 1): its: list[tuple[int, int]] = [] for (sx, sy), (bx, by) in sensor_to_beacon.items(): d = abs(sx - bx) + abs(sy - by) dx = d - abs(sy - y) if dx >= 0: its.append((max(0, sx - dx), min(sx + dx, xy_max))) its = sorted(its) _, e = its[0] for si, ei in its[1:]: if si > e + 1: return si - 1, y, 4_000_000 * (si - 1) + y if ei > e: e = ei return (0, 0, 0) def part2_cplex( sensor_to_beacon: dict[tuple[int, int], tuple[int, int]], xy_max: int ) -> tuple[int, int, int]: from docplex.mp.model import Model m = Model() x, y = m.continuous_var_list(2, ub=xy_max, name=["x", "y"]) for (sx, sy), (bx, by) in sensor_to_beacon.items(): d = abs(sx - bx) + abs(sy - by) m.add_constraint(m.abs(x - sx) + m.abs(y - sy) >= d + 1, ctname=f"ct_{sx}_{sy}") m.set_objective("min", x + y) s = m.solve() vx = int(s.get_value(x)) vy = int(s.get_value(y)) return vx, vy, 4_000_000 * vx + vy lines = sys.stdin.read().splitlines() sensor_to_beacon: dict[tuple[int, int], tuple[int, int]] = {} for line in lines: r = parse.parse( "Sensor at x={sx}, y={sy}: closest beacon is at x={bx}, y={by}", line ) sensor_to_beacon[int(r["sx"]), int(r["sy"])] = (int(r["bx"]), int(r["by"])) xy_max = 4_000_000 if max(sensor_to_beacon) > (1_000, 0) else 20 row = 2_000_000 if max(sensor_to_beacon) > (1_000, 0) else 10 print(f"answer 1 is {part1(sensor_to_beacon, row)}") # x, y, a2 = part2_cplex(sensor_to_beacon, xy_max) x, y, a2 = part2_intervals(sensor_to_beacon, xy_max) print(f"answer 2 is {a2} (x={x}, y={y})")