LeetCode/java/spiral-matrix-iii.java

class Solution {
  private record Coord(int x, int y) {
    public void assign(int[] coord) {
      coord[0] = y;
      coord[1] = x;
    }

    public Coord add(Coord rhs) {
      return new Coord(x + rhs.x, y + rhs.y);
    }
  }

  private static final List<Coord> DIRECTIONS =
      Arrays.asList(new Coord(1, 0), new Coord(0, 1), new Coord(-1, 0), new Coord(0, -1));

  private boolean inBounds(int rows, int cols, Coord pos) {
    return pos.y() >= 0 && pos.y() < rows && pos.x() >= 0 && pos.x() < cols;
  }

  public int[][] spiralMatrixIII(int rows, int cols, int rStart, int cStart) {
    int[][] matrix = new int[rows * cols][2];

    var pos = new Coord(cStart, rStart);
    for (int i = 0, step = 1, direction = 0; i < matrix.length; ++step) {
      for (int j = 0; j < 2; ++j) {
        for (int k = 0; k < step; ++k) {
          if (inBounds(rows, cols, pos)) {
            pos.assign(matrix[i]);
            ++i;
          }

          pos = pos.add(DIRECTIONS.get(direction));
        }

        direction = (direction + 1) % 4;
      }
    }

    return matrix;
  }
}