Flood Fill — رنگ‌آمیزی موجی

from collections import deque

def flood_fill(grid, sr, sc, color):
    rows, cols = len(grid), len(grid[0])
    target = grid[sr][sc]
    if target == color: return

    queue = deque([(sr, sc)])
    grid[sr][sc] = color      # رنگ مبدأ

    dirs = [(0,1),(0,-1),(1,0),(-1,0)]

    while queue:
        r, c = queue.popleft()
        for dr, dc in dirs:
            nr, nc = r+dr, c+dc
            if 0<=nr<rows and 0<=nc<cols:
                if grid[nr][nc] == target:
                    grid[nr][nc] = color
                    queue.append((nr, nc))

    # O(R × C) — هر خانه یک‌بار بازدید می‌شود