Java matrix runtime error

Question

Exercise letter:

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

For example, Given the

Answer 1

Try this.

static int[][] DIRECTIONS = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};

static boolean movable(int r, int c, int height, int width, boolean[][] visited) {
    if (r < 0 || r >= height || c < 0 || c >= width)
        return false;
    return !visited[r][c];
}

public List spiralOrder(int[][] matrix) {
    List result = new ArrayList<>();
    int height = matrix.length;
    if (height == 0) return result;
    int width = matrix[0].length;
    if (width == 0) return result;
    boolean[][] visited = new boolean[height][width];
    int direction = 0;
    int r = 0, c = 0;
    for (int i = 0; i < width * height; ++i) {
        result.add(matrix[r][c]);
        visited[r][c] = true;
        int[] directions = DIRECTIONS[direction % DIRECTIONS.length];
        if (!movable(r + directions[0], c + directions[1], height, width, visited))
            directions = DIRECTIONS[++direction % DIRECTIONS.length];
        r += directions[0];
        c += directions[1];
    }
    return result;
}