240622 알파벳

static int r;
static int c;
static int answer;
static char[][] map;
static int[] dr = {1, -1, 0, 0};
static int[] dc = {0, 0, 1, -1};
static int[][] visit;

public static void main(String[] args) throws IOException {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	StringTokenizer st = new StringTokenizer(br.readLine());
	r = Integer.parseInt(st.nextToken());
	c = Integer.parseInt(st.nextToken());
	map = new char[r + 2][c + 2];
	visit = new int[r + 2][c + 2];
	
	for (int[] row : visit) {
		Arrays.fill(row, -1);
	}

	for (int i = 0; i < r; i++) {
		char[] temp = br.readLine().toCharArray();
		for (int j = 0; j < c; j++) {
			map[i + 1][j + 1] = temp[j];
		}
	}
	
	char wall = map[1][1];
	Arrays.fill(map[0], wall);
	Arrays.fill(map[r + 1], wall);
	for (int i = 0; i < r + 2; i++) {
		map[i][0] = map[i][c + 1] = wall;
	}
	
	answer = 0;
	dfsWithVisit(1, 1, 1, 1 << (map[1][1] - 'A'));
	System.out.println(answer);
}

static void dfsWithVisit(int cnt, int r, int c, int bit) {
	answer = Math.max(answer, cnt);
	if (answer == 26) return;

	visit[r][c] = bit;

	for (int i = 0; i < 4; i++) {
		int nr = r + dr[i];
		int nc = c + dc[i];
		if ((bit & (1 << (map[nr][nc] - 'A'))) == 0 &&
			(bit | (1 << (map[nr][nc] - 'A'))) != visit[nr][nc]) {
			dfsWithVisit(cnt + 1, nr, nc, bit | (1 << (map[nr][nc] - 'A')));
		}
	}
}

출처:https://www.acmicpc.net/problem/1987