Amazon VO 面试真题解析：Flood Fill in a 2-Color Bitmap | BFS / DFS 经典题

Given a 2-dimensional 2-color bitmap, write a function to implement flood fill, e.g. the bucket in MS Paint. Assume that the fill will only fill white pixels with black.

The function should take the following parameters:

• A 2D array of booleans representing the pixels in the bitmap
• The X and Y position of the start point for the fill

So for example, in Java:

public void floodFill(boolean[][] bitmap, int xStart, int yStart)

这道题本质上是经典的 Flood Fill（泛洪填充）问题：从给定起点出发，把所有与起点连通、且颜色为白色的像素改成黑色。解法通常使用 DFS 或 BFS，从起点向四个方向扩展，遇到越界、非白色像素或已经访问过的像素就停止。关键点是正确处理连通性和边界条件，避免重复遍历。