Java Program to Implement Flood Fill Algorithm

This is a Java Program to Implement Flood Fill Algorithm. Flood fill, also called seed fill, is an algorithm that determines the area connected to a given node in a multi-dimensional array. It is used in the “bucket” fill tool of paint programs to fill connected, similarly-colored areas with a different color, and in games such as Go and Minesweeper for determining which pieces are cleared. When applied on an image to fill a particular bounded area with color, it is also known as boundary fill. Here ‘P’ is for passage, ‘O’ for obstacle and ‘W’ for water flow.

Here is the source code of the Java Program to Implement Flood Fill Algorithm. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

/**
 * Java Program to Implement Flood Fill Algorithm
 **/
 
import java.util.Scanner;
import java.util.Arrays;
 
/** Class FloodFill **/
public class FloodFill
{
    /** Function to fill grid **/
    private void fillGrid(char[][] arr, int r, int c) 
    {
        if (arr[r] == 'P')
        {
            arr[r] = 'W';
            display(arr);
 
            fillGrid(arr, r + 1, c);
            fillGrid(arr, r - 1, c);
            fillGrid(arr, r, c + 1);
            fillGrid(arr, r, c - 1);
        }
    }
    /** Function to display grid **/
    private void display(char[][] arr)
    {
        System.out.println("\nGrid : ");
        for (int i = 1; i < arr.length - 1; i++)
        {
            for (int j = 1; j < arr[i].length - 1; j++)
                System.out.print(arr[i][j] +" ");
            System.out.println();
        }
    }
 
    /** Main method **/
    public static void main(String[] args) 
    {
        Scanner scan = new Scanner( System.in );        
        System.out.println("Flood Fill Test\n");
 
        /** Accept dimensions **/
        System.out.println("Enter dimensions of grid");
        int M = scan.nextInt();
        int N = scan.nextInt();
 
        /** make grid with border as obstacle to avoid boundary conditions **/
        char[][] arr = new char[M + 2][N + 2];
        for (int i = 0; i < M + 2; i++)
            Arrays.fill(arr[i], 'O');
 
        /** Accept grid **/
        System.out.println("Enter grid with 'P' for passage and 'O' for obstacle");
 
        for (int i = 1; i < M + 1; i++)
            for (int j = 1; j < N + 1; j++)
                arr[i][j] = scan.next().charAt(0);    
 
        System.out.println("Enter coordinates to start ");
        int sr = scan.nextInt();
        int sc = scan.nextInt();
 
        if (arr[sr][sc] != 'P')
        {
            System.out.println("Invalid coordinates");
            System.exit(0);
        }
 
        FloodFill ff = new FloodFill();
        ff.fillGrid(arr, sr, sc);    
 
    }    
}

Flood Fill Test
 
Enter dimensions of grid
5 5
Enter grid with 'P' for passage and 'O' for obstacle
P P P P P
O P O P O
O O P P O
P P P O O
P O O O O
Enter coordinates to start
3 3
 
Grid :
P P P P P
O P O P O
O O W P O
P P P O O
P O O O O
 
Grid :
P P P P P
O P O P O
O O W P O
P P W O O
P O O O O
 
Grid :
P P P P P
O P O P O
O O W P O
P W W O O
P O O O O
 
Grid :
P P P P P
O P O P O
O O W P O
W W W O O
P O O O O
 
Grid :
P P P P P
O P O P O
O O W P O
W W W O O
W O O O O
 
Grid :
P P P P P
O P O P O
O O W W O
W W W O O
W O O O O
 
Grid :
P P P P P
O P O W O
O O W W O
W W W O O
W O O O O
 
Grid :
P P P W P
O P O W O
O O W W O
W W W O O
W O O O O
 
Grid :
P P P W W
O P O W O
O O W W O
W W W O O
W O O O O
 
Grid :
P P W W W
O P O W O
O O W W O
W W W O O
W O O O O
 
Grid :
P W W W W
O P O W O
O O W W O
W W W O O
W O O O O
 
Grid :
P W W W W
O W O W O
O O W W O
W W W O O
W O O O O
 
Grid :
W W W W W
O W O W O
O O W W O
W W W O O
W O O O O