733. Flood Fill

Given an image as a grid of colors, a starting pixel (sr, sc) and a color, recolor the starting pixel and every pixel 4-directionally connected to it that has the same original color.

Same idea, iteratively: paint a pixel as soon as it is queued so it is never queued twice.

1function floodFill(image: number[][], sr: number, sc: number, color: number): number[][] {
2  const start = image[sr][sc];
3  if (start === color) return image;
4  image[sr][sc] = color;
5  const queue = [[sr, sc]];
6  while (queue.length) {
7    const [r, c] = queue.shift()!;
8    for (const [x, y] of [[r + 1, c], [r - 1, c], [r, c + 1], [r, c - 1]])
9      if (image[x]?.[y] === start) { image[x][y] = color; queue.push([x, y]); }
10  }
11  return image;
12}

start = 1color = 2

image

1	1	1	0
1	2	0	0
1	0	1	1
0	1	1	1

queue

(1,1)

Paint (1, 1) and queue it.

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