====== 미세먼지 안녕! ======

===== 풀이 =====
  * 그냥 구현이 번거로운 시뮬레이션 문제.
  * 시키는대로 미세먼지의 확산과, 공기청정기의 이동을 구현하고, 이것을 T초동안 반복하면 된다. 총 시간복잡도는 O(T*r*c)
  * T초동안 매번 각 셀에서 인접한 셀들의 좌표를 계산하는 것을 피하기 위해서, 인접한 셀들의 좌표들을 처음 계산한 뒤 그래프 형태로 저장해서 사용했다.

===== 코드 =====
<dkpr py>
"""Solution code for "BOJ 17144. 미세먼지 안녕!".

- Problem link: https://www.acmicpc.net/problem/17144
- Solution link: http://www.teferi.net/ps/problems/boj/17144

Tags: [Implementation]
"""

import itertools

CLEANER = -1


def compute_diffusion(R, C, cleaner1, cleaner2):
    cycle1 = list(
        itertools.chain(
            range(cleaner1 - C, 0, -C),  # up
            range(C - 1),  # right
            range(C - 1, cleaner1 + C, C),  # down
            range(cleaner1 + C - 2, cleaner1 - 1, -1)  # left
        ))
    cycle2 = list(
        itertools.chain(
            range(cleaner2 + C, R * C, C),  # down
            range((R - 1) * C + 1, R * C - 1),  # right
            range(R * C - 1, cleaner2, -C),  # up
            range(cleaner2 + C - 2, cleaner2 - 1, -1)  # left
        ))
    return list(zip(cycle1[1:], cycle1)) + list(zip(cycle2[1:], cycle2))


def compute_adj_graph(R, C, cleaner1, cleaner2):
    adj_positions = []
    deltas = ((-1, 0), (1, 0), (0, -1), (0, 1))
    for row in range(R):
        for col in range(C):
            adj_positions.append([
                adj for dr, dc in deltas
                if (0 <= (nr := row + dr) < R and 0 <= (nc := col + dc) < C and
                    (adj := nr * C + nc) not in (cleaner1, cleaner2))
            ])
    return adj_positions


def main():
    R, C, T = [int(x) for x in input().split()]
    grid_cur = []
    for _ in range(R):
        grid_cur.extend(int(x) for x in input().split())

    cleaner1 = grid_cur.index(CLEANER)
    cleaner2 = cleaner1 + C
    grid_cur[cleaner1] = grid_cur[cleaner2] = 0
    diffusion = compute_diffusion(R, C, cleaner1, cleaner2)
    adj_positions = compute_adj_graph(R, C, cleaner1, cleaner2)

    for _ in range(T):
        grid_prev, grid_cur = grid_cur, [0] * (R * C)
        for pos, val, adj_pos in zip(range(R * C), grid_prev, adj_positions):
            if val == 0:
                continue
            dif = val // 5
            for p in adj_pos:
                grid_cur[p] += dif
                val -= dif
            grid_cur[pos] += val
        for prev, cur in diffusion:
            grid_cur[cur] = grid_cur[prev]

    print(sum(grid_cur))


if __name__ == '__main__':
    main()
</dkpr>

{{tag>BOJ ps:problems:boj:골드_4}}