Flood Fill

An image is a grid of integers (pixel colours). Starting from pixel (sr, sc), recolour it and every pixel connected to it up, down, left or right that has the same original colour as the start. Return the image.

This is the paint-bucket tool: diagonal pixels don't count.

Example 1

Input: image = [[1,1,1],[1,1,0],[1,0,1]],
       sr = 1, sc = 1, color = 2
Output: [[2,2,2],[2,2,0],[2,0,1]]

The bottom-right 1 only touches the region diagonally, so it keeps its colour.

Example 2

Input: image = [[0,0,0],[0,0,0]],
       sr = 0, sc = 0, color = 0
Output: [[0,0,0],[0,0,0]]

The new colour equals the old one: nothing changes.

Example 3

Input: image = [[0,0,0],[0,1,1]],
       sr = 1, sc = 1, color = 3
Output: [[0,0,0],[0,3,3]]

Constraints

• 1 <= rows, cols <= 150
• 0 <= image[r][c], color < 2^16
• (sr, sc) is inside the image
• Big regions are tested: a recursive DFS may exceed Python's recursion limit, so prefer a stack or queue.