230407 리코쳇 로봇

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

private int n;
private int m;

private static class Location {
    final int x;
    final int y;
    final int depth;

    public Location(int x, int y, int depth) {
        this.x = x;
        this.y = y;
        this.depth = depth;
    }
}

public int solution(String[] board) {
    n = board.length;
    m = board[0].length();

    Location robot = null;
    Location goal = null;

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            char ch = board[i].charAt(j);

            if (ch == 'R') {
                robot = new Location(i, j, 0);
            } else if (ch == 'G') {
                goal = new Location(i, j, 0);
            }
        }
    }

    return bfs(board, robot, goal);
}

private int bfs(String[] board, Location robot, Location goal) {
    Queue<Location> queue = new LinkedList<>();
    queue.add(robot);

    boolean[][] visited = new boolean[n][m];
    visited[robot.x][robot.y] = true;

    while (!queue.isEmpty()) {
        Location current = queue.poll();

        if (current.x == goal.x && current.y == goal.y) {
            return current.depth;
        }

        for (int i = 0; i < 4; i++) {
            int nx = current.x;
            int ny = current.y;

            while (inBounds(nx, ny) && board[nx].charAt(ny) != 'D') {
                nx += dx[i];
                ny += dy[i];
            }

            nx -= dx[i];
            ny -= dy[i];

            if (visited[nx][ny]) {
                continue;
            }

            visited[nx][ny] = true;
            queue.add(new Location(nx, ny, current.depth + 1));
        }
    }

    return -1;
}

private boolean inBounds(int x, int y) {
    return x >= 0 && y >= 0 && x < n && y < m;
}

출처:https://school.programmers.co.kr/learn/courses/30/lessons/169199