FloodFill.java

package com.thealgorithms.backtracking;

/**
 * Java program for Flood fill algorithm.
 * @author Akshay Dubey (<a href="https://github.com/itsAkshayDubey">Git-Akshay Dubey</a>)
 */
public final class FloodFill {
    private FloodFill() {
    }

    /**
     * Get the color at the given coordinates of a 2D image
     *
     * @param image The image to be filled
     * @param x The x co-ordinate of which color is to be obtained
     * @param y The y co-ordinate of which color is to be obtained
     */

    public static int getPixel(final int[][] image, final int x, final int y) {
        return image[x][y];
    }

    /**
     * Put the color at the given coordinates of a 2D image
     *
     * @param image The image to be filled
     * @param x The x co-ordinate at which color is to be filled
     * @param y The y co-ordinate at which color is to be filled
     */
    public static void putPixel(final int[][] image, final int x, final int y, final int newColor) {
        image[x][y] = newColor;
    }

    /**
     * Fill the 2D image with new color
     *
     * @param image The image to be filled
     * @param x The x co-ordinate at which color is to be filled
     * @param y The y co-ordinate at which color is to be filled
     * @param newColor The new color which to be filled in the image
     * @param oldColor The old color which is to be replaced in the image
     */
    public static void floodFill(final int[][] image, final int x, final int y, final int newColor, final int oldColor) {
        if (newColor == oldColor || x < 0 || x >= image.length || y < 0 || y >= image[x].length || getPixel(image, x, y) != oldColor) {
            return;
        }

        putPixel(image, x, y, newColor);

        /* Recursively check for horizontally & vertically adjacent coordinates */
        floodFill(image, x + 1, y, newColor, oldColor);
        floodFill(image, x - 1, y, newColor, oldColor);
        floodFill(image, x, y + 1, newColor, oldColor);
        floodFill(image, x, y - 1, newColor, oldColor);

        /* Recursively check for diagonally adjacent coordinates  */
        floodFill(image, x + 1, y - 1, newColor, oldColor);
        floodFill(image, x - 1, y + 1, newColor, oldColor);
        floodFill(image, x + 1, y + 1, newColor, oldColor);
        floodFill(image, x - 1, y - 1, newColor, oldColor);
    }
}