240808 배열에서 이동

static int n;
static int left;
static int right;
static boolean valid;
static int[][] altitudes;
static boolean[][] visited;
static final int[][] directions = { { -1, 0 }, { 1, 0 }, { 0, -1 }, { 0, 1 } };

public static void main(String[] args) throws IOException {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
	n = Integer.parseInt(br.readLine());
	altitudes = new int[n][n];
	HashSet<Integer> altitudeSet = new HashSet<>();
	StringTokenizer st;
	int answer = 200;

	for (int i = 0; i < n; i++) {
		st = new StringTokenizer(br.readLine());
		for (int j = 0; j < n; j++) {
			altitudes[i][j] = Integer.parseInt(st.nextToken());
			altitudeSet.add(altitudes[i][j]);
		}
	}

	ArrayList<Integer> altitudeList = new ArrayList<>(altitudeSet);
	Collections.sort(altitudeList);

	int lIndex = 0;
	int rIndex = 0;
	int startAltitude = altitudes[0][0];
	while (altitudeList.get(rIndex) < startAltitude)
		rIndex++;

	while (lIndex <= rIndex && rIndex < altitudeList.size()) {
		left = altitudeList.get(lIndex);
		if (startAltitude < left)
			break;
		right = altitudeList.get(rIndex);

		visited = new boolean[n][n];
		visited[0][0] = true;
		valid = false;
		dfs(0, 0);

		if (valid) {
			answer = Math.min(answer, right - left);
			lIndex++;
		} else {
			rIndex++;
		}
	}

	bw.write(Integer.toString(answer));
	bw.flush();
}

static void dfs(int r, int c) {
	if (r == n - 1 && c == n - 1) {
		valid = true;
		return;
	}

	for (int[] direction : directions) {
		int nr = r + direction[0];
		int nc = c + direction[1];
		if (isInBounds(nr, nc) && !visited[nr][nc]) {
			visited[nr][nc] = true;
			int nextAltitude = altitudes[nr][nc];
			if (left <= nextAltitude && nextAltitude <= right) {
				dfs(nr, nc);
			}
		}
	}
}

static boolean isInBounds(int r, int c) {
	return r >= 0 && r < n && c >= 0 && c < n;
}

출처:https://www.acmicpc.net/problem/1981