In a paint program, a “flood fill” fills all empty pixels of a drawing with a given color, stopping when it reaches occupied pixels. In this exercise, you will implement a simple variation of this algorithm, flood-filling a 10 × 10 array of integers that are initially 0. Prompt for the starting row and column. Push the (row, column) pair on a stack. (You will need to provide a simple Pair class.)

Then repeat the following operations until the stack is empty.

• Pop off the (row, column) pair from the top of the stack.

• If it has not yet been filled, fill it now. (Fill in numbers 1, 2, 3, and so on, to show the order in which the square is filled.)

• Push the coordinates of any unfilled neighbors in the north, east, south, or west direction on the stack.

public class FloodFillDemo 
{
   public static void main(String[] args)
   {
      Grid gr = new Grid();
      gr.floodfill(3, 4);
      System.out.println(gr.toString());
   }
}

public class FloodFillTester
{
   public static void main(String[] args)
   {
      Grid gr = new Grid();
      gr.floodfill(3, 4);
      String[] rows = gr.toString().split("\n");
      System.out.println(rows[2]);
      System.out.println("Expected: 15 12  9  6  2 81 79 77 75 73");
      System.out.println(rows[3]);
      System.out.println("Expected: 14 11  8  5  1  3 78 76 74 72");
      System.out.println(rows[4]);
      System.out.println("Expected: 16 13 10  7  4 63 65 67 69 71");
   }
}