#!/usr/bin/env python import itertools import sys from copy import deepcopy from typing import Iterator, List, Set, Tuple Grid = List[List[int]] Point = Tuple[int, int] def solve(input: List[str]) -> int: levels = [[int(c) for c in line] for line in input] def step(levels: Grid) -> Tuple[Grid, int]: # First step, increase levels levels = [[l + 1 for l in line] for line in levels] def excited(levels: Grid) -> Set[Point]: return set( (i, j) for i in range(len(levels)) for j in range(len(levels[i])) if levels[i][j] > 9 ) def neighbours_of(point: Point) -> Iterator[Point]: for dx, dy in itertools.product((-1, 0, 1), repeat=2): if dx == 0 and dy == 0: continue x = point[0] + dx y = point[1] + dy if x < 0 or x >= len(levels): continue if y < 0 or y >= len(levels[x]): continue yield x, y # Second step, do flashes has_flashed: Set[Point] = set() while len(flashes := (excited(levels) - has_flashed)) > 0: for (i, j) in flashes: has_flashed.add((i, j)) for x, y in neighbours_of((i, j)): levels[x][y] += 1 # Finally, bring back energy levels to 0 for i, j in has_flashed: levels[i][j] = 0 return levels, len(has_flashed) res = 0 for __ in range(100): levels, flashes = step(levels) res += flashes return res def main() -> None: input = [line.strip() for line in sys.stdin.readlines()] print(solve(input)) if __name__ == "__main__": main()