class Solution(object):

def floodFill(self, image, sr, sc, newColor):

stack = [(sr, sc)]

originColor = image[sr][sc]

while stack:

i, j = stack.pop()

if image[i][j]==newColor or image[i][j]!=originColor: continue

image[i][j] = newColor

if i+1<len(image): stack.append((i+1, j))

if 0<=i-1: stack.append((i-1, j))

if j+1<len(image[0]): stack.append((i, j+1))

if 0<=j-1: stack.append((i, j-1))

return image

"""

DFS the `image`.

If the color is newColor, we don't need to see.

If the color is not originalColor, we don't need to see, too.

Else we paint the node to newColor.

Time: O(N).

Space: O(1).

"""