// Implements a 2-D array of characters

public class CharMatrix
{
  public final char SPACE = ' ';
  private char[][] grid;

  // Constructor: creates a grid with dimensions rows, cols,
  // and fills it with spaces
  public CharMatrix(int rows, int cols)
  {
    grid = new char[rows][cols];
    fillRect(0, 0, rows-1, cols-1, SPACE);
  }

  // Constructor: creates a grid with dimensions rows , cols ,
  // and fills it with the fill  character
  public CharMatrix(int rows, int cols, char fill)
  {
    grid = new char[rows][cols];
    fillRect(0, 0, rows-1, cols-1, fill);
  }

  // Returns the number of rows in grid
  public int numRows()
  {
    return grid.length;
  }

  // Returns the number of columns in grid
  public int numCols()
  {
    return grid[0].length;
  }

  // Returns the character at row, col location
  public char charAt(int row, int col)
  {
    return grid[row][col];
  }

  // Sets the character at row, col location to ch
  public void setCharAt(int row, int col, char ch)
  {
    grid[row][col] = ch;
  }

  // Returns true if the character at row, col is a space,
  // false otherwise
  public boolean isEmpty(int row, int col)
  {
    return charAt(row, col) == SPACE;
  }

  // Fills the given rectangle with fill  characters.
  // row0, col0 is the upper left corner and row1, col1 is the
  // lower right corner of the rectangle.
  public void fillRect(int row0, int col0, int row1, int col1, char fill)
  {
    for (int r = row0; r <= row1; r++)
    {
      for (int c = col0; c <= col1; c++)
      {
        setCharAt(r, c, fill);
      }
    }
  }

  // Fills the given rectangle with SPACE characters.
  // row0, col0 is the upper left corner and row1, col1 is the
  // lower right corner of the rectangle.
  public void clearRect(int row0, int col0, int row1, int col1)
  {
    fillRect(row0, col0, row1, col1, SPACE);
  }

  // Returns the count of all non-space characters in row 
  public int countInRow(int row)
  {
    int count = 0;

    for (int c = 0; c < numCols(); c++)
      if (!isEmpty(row, c))
        count++;

    return count;
  }

  // Returns the count of all non-space characters in col 
  public int countInCol(int col)
  {
    int count = 0;

    for (int r = 0; r < numRows(); r++)
      if (!isEmpty(r, col))
        count++;

    return count;
  }
}