Won't pass validation

Question about the task

Under discussion

My approach to this was to create a Pixel class (so that I have an object that stores both an x and y coordinate), and add and remove Pixel objects from ArrayLists. The general process is like this: 1. Maintain an ArrayList of Pixel objects that are confirmed to be changing color called pixelsToChange. 2. Maintain an ArrayList of Pixel objects still to be tested called pixelQueue. 3. Maintain an ArrayList of Pixel objects that have been tested (regardless of result) to prevent re-testing called pixelsToIgnore. 4. Add the starting pixel to pixelsToChange and pixelsToIgnore. 5. Add all adjacent pixels to pixelQueue and pixelsToIgnore, then enter while loop: 6.a. Get and remove the next Pixel in pixelQueue 6.b. If it should be changed, add it to pixelsToChange, and then 6.c. Add its adjacent pixels to pixelQueue, ignoring any that are already in pixelsToIgnore 7. When pixelQueue is empty, the loop ends. 8. Iterate through pixelsToChange, and get each Pixel's x and y values, and change the value of image[y][x] appropriately. However, it doesn't pass validation. I'm looking for some hints as to where it may be going wrong.

While developing a new version of a popular graphics editor, it has become necessary to implement the ability to fill an area of an image with a specified color.

Implement a paintFill method in the PhotoPaint class so that it:
- returns false if the color of the starting point (the coordinates are passed as arguments) matches the fill color or if the starting coordinates are beyond the bounds of the array.
- modifies the input array and returns true if the fill can still be performed.

The point with coordinates (x, y) corresponds to the array element with indices [y][x].

P.S. If the fill algorithm isn't clear, practice using Paint.

Requirements:

The paintFill method must return false if the passed coordinates are beyond the bounds of the image.
The paintFill method must return false if the color of the starting point is the same as the fill color.
If possible, the paintFill method must return true and correctly modify the image.
The paintFill method must be public.

package com.codegym.task.task39.task3905; /* Fill 'er up */ public class Solution { public static void main(String[] args) { } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

4 May 2023, 20:02

I think a recursive method would make more sense here: You just need to the recursive method to basically work the same with one additional key detail: the very first color at x,y that was there when paintfill is called: so, I have something like this code as an idea:

public boolean paintFill(Color[][] image, int x, int y, Color desiredColor) {
   if(x < 0 || y < 0 || y >= image.length || x >= image[0].length || image[y][x] == desiredColor) {
      return false;
   }
   Color original = /*get color at [y][x]*/;
   recusion(image, x, y, original, desiredColor);
   return true;
}

void recursion((Color[][] image, int x, int y, Color original, Color desiredColor) {
   if(x < 0 || y < 0 || y >= image.length || x >= image[0].length || image[y][x] != original) {
      return;
   }
   /*change color to desiredColor at [y][x]*/;

   recusion(image, x -1, y, original, desiredColor);
   recusion(image, x+1, y, original, desiredColor);
   recusion(image, x, y-1, original, desiredColor);
   recusion(image, x, y+1, original, desiredColor);
}

Thomas

Level 41 , Bayreuth, Germany

4 May 2023, 20:37

This is a fancy way to fill the entire array, unless you try to consider the original color... :)

public boolean paintFill(Color[][] image, int x, int y, Color desiredColor) {
   ...
   Color original = /*get color at [y][x]*/; // and check if this color == original color, don't change other colors
   ...
}

void recursion((Color[][] image, int x, int y, Color original, Color desiredColor) {
   ...
   /*change color to desiredColor at [y][x]*/; // but make sure this color == original color, don't change other colors
   ....
}

Guadalupe Gagnon

Level 37 , Tampa, United States

4 May 2023, 22:54

I just typed it up quickly as an example., it will need to be debugged, however im sure it acceptable or very close to it. In paintFill the last Boolean on line 2 checks if the color is the same and will return false if true. In recursion the last Boolean on line 11 checks that the value at x,y is NOT the original color so any other color but the original color will return. Its very similar to the minesweeper game algorithm when you click an empty square.

Thomas

Level 41 , Bayreuth, Germany

4 May 2023, 23:40

ha, right, haven't seen the last condition in lines 2 and 11. That of course looks cool and should work properly (without having tested it ;) )

Guadalupe Gagnon

Level 37 , Tampa, United States

5 May 2023, 03:07

Its a bit annoying that the comments cut off code instead of wrapping it so it is all visible.

Justin Smith

Level 41 , Greenfield, USA, United States

5 May 2023, 23:03

Yep, I can see now this is definitely a far better approach.