240318 석유 시추

private static final int[] dx = new int[] { 0, 1, 0, -1 };
private static final int[] dy = new int[] { -1, 0, 1, 0 };
private Map<Integer, Integer> answerMap;

public int solution(int[][] land) {
	answerMap = new HashMap<>();
	for (int i = 0; i < land.length; i++) {
		for (int j = 0; j < land[i].length; j++) {
			if (land[i][j] == 1) {
				Set<Integer> set = new HashSet<>();
				bfs(land, new int[] { i, j }, set);
			}
		}
	}
	return answerMap.values()
			.stream()
			.mapToInt(Integer::intValue)
			.max()
			.orElse(0);
}

private void bfs(int[][] map, int[] now, Set<Integer> set) {
	int size = 1;
	Queue<int[]> queue = new LinkedList<>();
	queue.add(now);
	set.add(now[1]);
	map[now[0]][now[1]] = 2;
	while (!queue.isEmpty()) {
		int[] next = queue.poll();
		int x = next[0];
		int y = next[1];
		for (int i = 0; i < 4; i++) {
			int nx = x + dx[i];
			int ny = y + dy[i];
			if (nx >= 0 && nx < map.length && ny >= 0 && ny < map[0].length && map[nx][ny] == 1) {
				map[nx][ny] = 2;
				queue.add(new int[] { nx, ny });
				set.add(ny);
				size++;
			}
		}
	}
	for (int y : set) {
		answerMap.put(y, answerMap.getOrDefault(y, 0) + size);
	}
}

출처:https://school.programmers.co.kr/learn/courses/30/lessons/250136