BOJ - 3197 - 백조의 호수

import sys
from collections import deque

def BFS(water, swan, W, H, lake):
    dx = [0, 0, -1, 1]
    dy = [1, -1, 0, 0]

    endX, endY = swan.pop()

    time = 1
    while swan:
        temp = deque()
        while water:
            x, y = water.popleft()
            for i in range(4):
                nx = x + dx[i]
                ny = y + dy[i]

                if 0 <= nx < H and 0 <= ny < W:
                    if lake[nx][ny] == 'X':
                        lake[nx][ny] = '.'
                        temp.append((nx, ny))
        water = temp

        temp = deque()
        while swan:
            x, y = swan.popleft()

            if x == endX and y == endY:
                return time

            if lake[x][y] == 'L':
                lake[x][y] = time

            for i in range(4):
                nx = x + dx[i]
                ny = y + dy[i]

                if 0 <= nx < H and 0 <= ny < W:
                    if lake[nx][ny] == '.' or lake[nx][ny] == 'L':
                        lake[nx][ny] = time
                        swan.append((nx, ny))
                        temp.append((nx, ny))
        swan = temp
        time += 1
    return time

def solution():
    lake = []
    water = deque()
    swan = deque()
    H, W = map(int, sys.stdin.readline().split())

    for _ in range(H):
        lake.append(list(str(sys.stdin.readline().strip())))

    for i in range(H):
        for j in range(W):
            if lake[i][j] == "L":
                swan.append((i, j))
                water.append((i, j))
            elif lake[i][j] == ".":
                water.append((i, j))


    print(BFS(water, swan, W, H, lake))

solution()

https://www.acmicpc.net/problem/3197