백준 온라인 저지, BFS / 3055번: 탈출 (파이썬 / , 백준 골드문제)

문제

사악한 암흑의 군주 이민혁은 드디어 마법 구슬을 손에 넣었고, 그 능력을 실험해보기 위해 근처의 티떱숲에 홍수를 일으키려고 한다. 이 숲에는 고슴도치가 한 마리 살고 있다. 고슴도치는 제일 친한 친구인 비버의 굴로 가능한 빨리 도망가 홍수를 피하려고 한다.

티떱숲의 지도는 R행 C열로 이루어져 있다. 비어있는 곳은 '.'로 표시되어 있고, 물이 차있는 지역은 '*', 돌은 'X'로 표시되어 있다. 비버의 굴은 'D'로, 고슴도치의 위치는 'S'로 나타내어져 있다.

매 분마다 고슴도치는 현재 있는 칸과 인접한 네 칸 중 하나로 이동할 수 있다. (위, 아래, 오른쪽, 왼쪽) 물도 매 분마다 비어있는 칸으로 확장한다. 물이 있는 칸과 인접해있는 비어있는 칸(적어도 한 변을 공유)은 물이 차게 된다. 물과 고슴도치는 돌을 통과할 수 없다. 또, 고슴도치는 물로 차있는 구역으로 이동할 수 없고, 물도 비버의 소굴로 이동할 수 없다.

티떱숲의 지도가 주어졌을 때, 고슴도치가 안전하게 비버의 굴로 이동하기 위해 필요한 최소 시간을 구하는 프로그램을 작성하시오.

고슴도치는 물이 찰 예정인 칸으로 이동할 수 없다. 즉, 다음 시간에 물이 찰 예정인 칸으로 고슴도치는 이동할 수 없다. 이동할 수 있으면 고슴도치가 물에 빠지기 때문이다. 

입력

첫째 줄에 50보다 작거나 같은 자연수 R과 C가 주어진다.

다음 R개 줄에는 티떱숲의 지도가 주어지며, 문제에서 설명한 문자만 주어진다. 'D'와 'S'는 하나씩만 주어진다.

출력

첫째 줄에 고슴도치가 비버의 굴로 이동할 수 있는 가장 빠른 시간을 출력한다. 만약, 안전하게 비버의 굴로 이동할 수 없다면, "KAKTUS"를 출력한다.

제한

예제 입력 1

3 3
D.*
...
.S.

예제 출력 1

3

예제 입력 2

3 3
D.*
...
..S

예제 출력 2

KAKTUS

예제 입력 3

3 6
D...*.
.X.X..
....S.

예제 출력 3

6

예제 입력 4

5 4
.D.*
....
..X.
S.*.
....

예제 출력 4

4

힌트

[{"problem_id":"3055","problem_lang":"0","title":"\ud0c8\ucd9c","description":"<p>\uc0ac\uc545\ud55c \uc554\ud751\uc758 \uad70\uc8fc \uc774\ubbfc\ud601\uc740 \ub4dc\ub514\uc5b4 \ub9c8\ubc95 \uad6c\uc2ac\uc744 \uc190\uc5d0 \ub123\uc5c8\uace0, \uadf8 \ub2a5\ub825\uc744 \uc2e4\ud5d8\ud574\ubcf4\uae30 \uc704\ud574 \uadfc\ucc98\uc758 \ud2f0\ub5b1\uc232\uc5d0 \ud64d\uc218\ub97c \uc77c\uc73c\ud0a4\ub824\uace0 \ud55c\ub2e4. \uc774 \uc232\uc5d0\ub294 \uace0\uc2b4\ub3c4\uce58\uac00 \ud55c \ub9c8\ub9ac \uc0b4\uace0 \uc788\ub2e4. \uace0\uc2b4\ub3c4\uce58\ub294 \uc81c\uc77c \uce5c\ud55c \uce5c\uad6c\uc778 \ube44\ubc84\uc758 \uad74\ub85c \uac00\ub2a5\ud55c \ube68\ub9ac \ub3c4\ub9dd\uac00 \ud64d\uc218\ub97c \ud53c\ud558\ub824\uace0 \ud55c\ub2e4.<\/p>\r\n\r\n<p>\ud2f0\ub5b1\uc232\uc758 \uc9c0\ub3c4\ub294 R\ud589 C\uc5f4\ub85c \uc774\ub8e8\uc5b4\uc838 \uc788\ub2e4. \ube44\uc5b4\uc788\ub294 \uacf3\uc740 &#39;.&#39;\ub85c \ud45c\uc2dc\ub418\uc5b4 \uc788\uace0, \ubb3c\uc774 \ucc28\uc788\ub294 \uc9c0\uc5ed\uc740 &#39;*&#39;, \ub3cc\uc740 &#39;X&#39;\ub85c \ud45c\uc2dc\ub418\uc5b4 \uc788\ub2e4. \ube44\ubc84\uc758 \uad74\uc740 &#39;D&#39;\ub85c, \uace0\uc2b4\ub3c4\uce58\uc758 \uc704\uce58\ub294 &#39;S&#39;\ub85c \ub098\ud0c0\ub0b4\uc5b4\uc838 \uc788\ub2e4.<\/p>\r\n\r\n<p>\ub9e4 \ubd84\ub9c8\ub2e4 \uace0\uc2b4\ub3c4\uce58\ub294 \ud604\uc7ac \uc788\ub294 \uce78\uacfc \uc778\uc811\ud55c \ub124 \uce78 \uc911 \ud558\ub098\ub85c \uc774\ub3d9\ud560 \uc218 \uc788\ub2e4. (\uc704, \uc544\ub798, \uc624\ub978\ucabd, \uc67c\ucabd) \ubb3c\ub3c4 \ub9e4 \ubd84\ub9c8\ub2e4 \ube44\uc5b4\uc788\ub294 \uce78\uc73c\ub85c \ud655\uc7a5\ud55c\ub2e4. \ubb3c\uc774 \uc788\ub294 \uce78\uacfc \uc778\uc811\ud574\uc788\ub294 \ube44\uc5b4\uc788\ub294 \uce78(\uc801\uc5b4\ub3c4 \ud55c \ubcc0\uc744 \uacf5\uc720)\uc740 \ubb3c\uc774 \ucc28\uac8c \ub41c\ub2e4. \ubb3c\uacfc \uace0\uc2b4\ub3c4\uce58\ub294 \ub3cc\uc744 \ud1b5\uacfc\ud560 \uc218 \uc5c6\ub2e4. \ub610, \uace0\uc2b4\ub3c4\uce58\ub294 \ubb3c\ub85c \ucc28\uc788\ub294 \uad6c\uc5ed\uc73c\ub85c \uc774\ub3d9\ud560 \uc218 \uc5c6\uace0, \ubb3c\ub3c4 \ube44\ubc84\uc758 \uc18c\uad74\ub85c \uc774\ub3d9\ud560 \uc218 \uc5c6\ub2e4.<\/p>\r\n\r\n<p>\ud2f0\ub5b1\uc232\uc758 \uc9c0\ub3c4\uac00 \uc8fc\uc5b4\uc84c\uc744 \ub54c, \uace0\uc2b4\ub3c4\uce58\uac00 \uc548\uc804\ud558\uac8c \ube44\ubc84\uc758 \uad74\ub85c \uc774\ub3d9\ud558\uae30 \uc704\ud574 \ud544\uc694\ud55c \ucd5c\uc18c \uc2dc\uac04\uc744 \uad6c\ud558\ub294 \ud504\ub85c\uadf8\ub7a8\uc744 \uc791\uc131\ud558\uc2dc\uc624.<\/p>\r\n\r\n<p>\uace0\uc2b4\ub3c4\uce58\ub294 \ubb3c\uc774 \ucc30 \uc608\uc815\uc778 \uce78\uc73c\ub85c \uc774\ub3d9\ud560 \uc218 \uc5c6\ub2e4. \uc989, \ub2e4\uc74c \uc2dc\uac04\uc5d0 \ubb3c\uc774 \ucc30 \uc608\uc815\uc778 \uce78\uc73c\ub85c \uace0\uc2b4\ub3c4\uce58\ub294 \uc774\ub3d9\ud560 \uc218 \uc5c6\ub2e4. \uc774\ub3d9\ud560 \uc218 \uc788\uc73c\uba74 \uace0\uc2b4\ub3c4\uce58\uac00 \ubb3c\uc5d0 \ube60\uc9c0\uae30 \ub54c\ubb38\uc774\ub2e4.&nbsp;<\/p>\r\n","input":"<p>\uccab\uc9f8 \uc904\uc5d0 50\ubcf4\ub2e4 \uc791\uac70\ub098 \uac19\uc740 \uc790\uc5f0\uc218 R\uacfc C\uac00 \uc8fc\uc5b4\uc9c4\ub2e4.<\/p>\r\n\r\n<p>\ub2e4\uc74c R\uac1c \uc904\uc5d0\ub294 \ud2f0\ub5b1\uc232\uc758 \uc9c0\ub3c4\uac00 \uc8fc\uc5b4\uc9c0\uba70, \ubb38\uc81c\uc5d0\uc11c \uc124\uba85\ud55c \ubb38\uc790\ub9cc \uc8fc\uc5b4\uc9c4\ub2e4. &#39;D&#39;\uc640 &#39;S&#39;\ub294 \ud558\ub098\uc529\ub9cc \uc8fc\uc5b4\uc9c4\ub2e4.<\/p>\r\n","output":"<p>\uccab\uc9f8 \uc904\uc5d0 \uace0\uc2b4\ub3c4\uce58\uac00 \ube44\ubc84\uc758 \uad74\ub85c \uc774\ub3d9\ud560 \uc218 \uc788\ub294 \uac00\uc7a5 \ube60\ub978 \uc2dc\uac04\uc744 \ucd9c\ub825\ud55c\ub2e4. \ub9cc\uc57d, \uc548\uc804\ud558\uac8c \ube44\ubc84\uc758 \uad74\ub85c \uc774\ub3d9\ud560 \uc218 \uc5c6\ub2e4\uba74, &quot;KAKTUS&quot;\ub97c \ucd9c\ub825\ud55c\ub2e4.<\/p>\r\n","hint":"","original":"0","html_title":"0","problem_lang_tcode":"Korean"},{"problem_id":"3055","problem_lang":"1","title":"SLIKAR","description":"<p>The evil emperor Cactus has in his possession the Magic Keg and has flooded the Enchanted Forest! The Painter and the three little hedgehogs now have to return to the Beaver&#39;s den where they will be safe from the water as quickly as possible!&nbsp;<\/p>\r\n\r\n<p>The map of the Enchanted Forest consists of R rows and C columns. Empty fields are represented by &#39;.&#39; characters, flooded fields by &#39;*&#39; and rocks by &#39;X&#39;. Additionally, the Beaver&#39;s den is represented by &#39;D&#39; and the Painter and the three little hedgehogs are shown as &#39;S&#39;.&nbsp;<\/p>\r\n\r\n<p>Every minute the Painter and the three little hedgehogs can move to 4 neighbouring fields (up, down, left or right). Every minute the flood expands as well so that all empty fields that have at least one common side with a flooded field become flooded as well. Neither water nor the Painter and the three little hedgehogs can pass through rocks. Naturally, the Painter and the three little hedgehogs cannot pass through flooded fields, and water cannot flood the Beaver&#39;s den.<\/p>\r\n\r\n<p>Write a program that will, given a map of the Enchanted Forest, output the shortest time needed for the Painter and the three little hedgehogs to safely reach the Beaver&#39;s den.<\/p>\r\n\r\n<p>Note: The Painter and the three little hedgehogs cannot move into a field that is about to be flooded (in the same minute).&nbsp;<\/p>\r\n","input":"<p>The first line of input will contain two integers, R and C, smaller than or equal to 50.&nbsp;<\/p>\r\n\r\n<p>The following R lines will each contain C characters (&#39;.&#39;, &#39;*&#39;, &#39;X&#39;, &#39;D&#39; or &#39;S&#39;). The map will contain exactly one &#39;D&#39; character and exactly one &#39;S&#39; character.&nbsp;<\/p>\r\n","output":"<p>Output the shortest possible time needed for the Painter and the three little hedgehogs to safely reach the Beaver&#39;s den. If this is impossible output the word &ldquo;KAKTUS&rdquo; on a line by itself.<\/p>\r\n","hint":"","original":"1","html_title":"0","problem_lang_tcode":"English"}]

접근 방법

- BFS를 활용해 물과 고슴도치의 위치를 상하좌우로 한칸씩 움직인다.
- 단 물부터 먼저 움직이고, 고슴도치를 움직이고, 매 초마다 동작하도록 한다.

코드

# https://www.acmicpc.net/problem/3055
# 접근방법
# BFS를 활용해 물과 고슴도치의 위치를 상하좌우로 한칸씩 움직인다.
# 단 물부터 먼저 움직이고, 고슴도치를 움직이고, 매 초마다 동작하도록 한다.
from collections import deque

r, c = map(int, input().split())
map_ = [[x for x in input()] for _ in range(r)]
hedgehog = deque([])
water = deque([])

for i in range(r):
    for j in range(c):
        if map_[i][j] == '*':
            water.append([i, j])
        elif map_[i][j] == 'S':
            hedgehog.append([i, j])
            map_[i][j] = 0
        elif map_[i][j] == 'D':
            x, y = i, j


def water_move():
    # 1초 마다 물 이동
    water_ = []
    while water:
        row, col = water.popleft()
        map_[row][col] = '*'
        for dr, dc in [[1, 0], [-1, 0], [0, 1], [0, -1]]:
            if 0<=row+dr<=r-1 and 0<=col+dc<=c-1:
                if map_[row+dr][col+dc] in ['.', 'S'] and [row_dr, col+dc] not in water_:
                    water_.append([row+dr, col+dc])
                    

    # 물을 다 이동시킨 뒤, 새로운 장소를 다시 water에 입력
    while water_:
        x = water_.pop()
        water.append(x)
    

def hedgehog_move():
    # 1초마다 고슴도치 이동
    hedgehog_ = []
    while hedgehog:
        row, col = hedgehog.popleft()
        for dr, dc in [[1, 0], [-1, 0], [0, 1], [0, -1]]:
            if 0<=row+dr<=r-1 and 0<=col+dc<=c-1:
                if map_[row+dr][col+dc] == '.' and [row+dr, col+dc] not in water:
                    hedgehog_.append([row+dr, col+dc])
                    map_[row+dr][col+dc] = map_[row][col] + 1
                elif map_[row+dr][col+dc] == 'D':
                    map_[row+dr][col+dc] = map_[row][col] + 1
                    return True

    # 고슴도치를 다 이동시킨 뒤, 새로운 자소를 다시 hedgehog에 입력
    while hedgehog_:
        x = hedgehog_.pop()
        hedgehog.append(x)

    return False

for time in range(1, 2501):
    if not hedgehog:
        break

    water_move()
    if hedgehog_move():
        break
if map_[x][y] == 'D':
    print('KAKTUS')
else:
    print(map_[x][y])