Hello,

Here’s my solution for the flood fill problem, found on LeetCode.

If you want me to write about certain topics please let me know in the comments, thank you!

``````"""
An image is represented by a 2-D array of integers, each integer representing the pixel
value of the image (from 0 to 65535).

Given a coordinate (sr, sc) representing the starting pixel (row and column) of the flood fill,
and a pixel value newColor, "flood fill" the image.

To perform a "flood fill", consider the starting pixel, plus any pixels connected 4-directionally
to the starting pixel of the same color as the starting pixel, plus any pixels connected 4-directionally
to those pixels (also with the same color as the starting pixel), and so on. Replace the color of all
of the aforementioned pixels with the newColor.

At the end, return the modified image.
"""
from typing import List, Tuple

class Solution:
def __init__(self):
self.visited = set()

def _set_pixel(self, image: List[List[int]], point: Tuple[int, int], value: int):
try:
image[point[0]][point[1]] = value
except IndexError:
pass

def _get_pixel(self, image: List[List[int]], point: Tuple[int, int]):
if point[0] < 0 or point[1] < 0:
return None
try:
return image[point[0]][point[1]]
except IndexError:
return None

def _floodFill(self, image: List[List[int]], point: Tuple[int, int], color: int, newColor: int) -> List[List[int]]:
pixel = self._get_pixel(image, point)
if pixel is not None and pixel == color and point not in self.visited:
self._set_pixel(image, point, newColor)
self._floodFill(image, (point[0], point[1] + 1), color, newColor)
self._floodFill(image, (point[0], point[1] - 1), color, newColor)
self._floodFill(image, (point[0] + 1, point[1]), color, newColor)
self._floodFill(image, (point[0] - 1, point[1]), color, newColor)

def floodFill(self, image: List[List[int]], sr: int, sc: int, newColor: int) -> List[List[int]]:
point = (sr, sc)
pixel = self._get_pixel(image, point)
self.visited = set()
if pixel is not None:
self._floodFill(image, point, pixel, newColor)
return image

if __name__ == '__main__':
s = Solution()

out = s.floodFill([[1,1,1],[1,1,0],[1,0,1]], 1, 1, 2)
print("Output", out)
assert out == [[2,2,2],[2,2,0],[2,0,1]]

out = s.floodFill([[0,0,0],[0,0,0]], 0, 0, 2)
print("Output", out)
assert out == [[2,2,2],[2,2,2]]

out = s.floodFill([[0,0,0],[0,1,1]], 1, 1, 1)
print("Output", out)
assert out == [[0, 0, 0], [0, 1, 1]]
``````