[백준] 7576번: 토마토

😎BACKJOON>7576번:토마토

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📘 문제풀이

미로찾기와 비슷하게 BFS 사용
다른점: 시작점이 하나가 아닌 여러개 가능

from collections import deque

m, n = map(int, input().split())
graph = [list(map(int, input().split())) for _ in range(n)]
visited= [[False] * m for _ in range(n)]

dx = [1, -1, 0, 0]
dy = [0, 0, 1, -1]

def tomato_bfs(graph, visited):
    queue = deque()
    
    for i in range(n):
        for j in range(m):
            if graph[i][j] == 1:
                queue.append((i, j))
                visited[i][j] = True        

    while queue:
        pop_x, pop_y = queue.popleft()
        
        for i in range(4):
            next_x = pop_x + dx[i]
            next_y = pop_y + dy[i]
            if next_x <= -1 or next_x >= n or next_y <= -1 or next_y >= m:
                continue
            if visited[next_x][next_y] != True and graph[next_x][next_y] == 0:
                queue.append((next_x,next_y))
                visited[next_x][next_y] = True
                graph[next_x][next_y] = graph[pop_x][pop_y] + 1

tomato_bfs(graph,visited)
graph_max = max(map(max, graph))
print(-1) if any(0 in i for i in graph) else print(graph_max-1)

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✏ 이론

2차원 배열 원소 포함 판단하기

#list에 0이 존재
if all(0 not in n for n in list):
        return True

#list에 0이 하나라도 존재
if any(0 in n for n in list):
        return True

2차원 배열에서 max, min 값 찾기

map을 이용

#Max
max_value = max(map(max, list))

#Min
min_value = min(map(min, list))