250515 피리 부는 사나이

public static void main(String[] args) throws IOException {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	StringTokenizer st = new StringTokenizer(br.readLine());
	int rowCount = Integer.parseInt(st.nextToken());
	int colCount = Integer.parseInt(st.nextToken());

	char[][] grid = new char[rowCount][colCount];
	for (int i = 0; i < rowCount; i++) {
		grid[i] = br.readLine().toCharArray();
	}

	int[][] visited = new int[rowCount][colCount];
	int safeZoneCount = 0;
	int visitId = 0;

	int[] dx = { 0, 1, 0, -1 };
	int[] dy = { 1, 0, -1, 0 };

	for (int r = 0; r < rowCount; r++) {
		for (int c = 0; c < colCount; c++) {
			if (visited[r][c] == 0) {
				visitId++;
				if (dfs(r, c, visitId, grid, visited, dx, dy, rowCount, colCount)) {
					safeZoneCount++;
				}
			}
		}
	}

	System.out.println(safeZoneCount);
}

private static boolean dfs(int r, int c, int visitId,
		char[][] grid, int[][] visited,
		int[] dx, int[] dy,
		int rowCount, int colCount) {
	if (visited[r][c] == visitId) {
		return true;
	}
	if (visited[r][c] != 0) {
		return false;
	}
	visited[r][c] = visitId;

	int dir = getDirection(grid[r][c]);
	int nr = r + dx[dir];
	int nc = c + dy[dir];

	if (nr < 0 || nr >= rowCount || nc < 0 || nc >= colCount) {
		return false;
	}
	return dfs(nr, nc, visitId, grid, visited, dx, dy, rowCount, colCount);
}

private static int getDirection(char ch) {
	switch (ch) {
		case 'R':
			return 0;
		case 'D':
			return 1;
		case 'L':
			return 2;
		case 'U':
			return 3;
		default:
			throw new IllegalArgumentException("Invalid direction: " + ch);
	}
}

출처:https://www.acmicpc.net/problem/16724