LeetCode 733. Flood Fill (Algorithm Explained)

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[biswamohandwari]

You have the ultimate power to make us understand complex problems very easily that's what makes you powerful. Your the best...

[vyshnavramesh]

1:21 number of islands, flood fill, rotten basically bfs n dfs algos

[tushargupta]

your mistake was a good thing to learn from

[ahmadalk]

this line saved my day thanks! I was going with stackOverFlow exception without it.
if ( image[sr][sc] == newColor ) return image;

[TheBsoncarty]

Idk if you read these comments anymore, but I want to say thanks dude. These videos that you've made have been vital to my ability to understand how to approach LeetCode questions.

[ruibinzhang]

The most blessed thing is that I am stuck with a question, but Nick has already solved it and made a video.

[kishoureb]

Thanks a lot for the clear explanation. Just keep doing this awesome work. It really means a lot to me.

[smellthel]

So there are 732 other episodes of this series?

[adityap]

You were right, this is almost identical to number of islands. Once I got this I figured that one out pretty quickly.

[thommy]

Keep doing that awesome work man! Got it instantly, your explanations are very clear.

[prathyushakadali]

Thanks so much for sharing this, but doesn't this cause repetition? for eg: void fill method is called for sr=1, sc=1, more than it is required.

[jacksingermusic]

What is the time and space complexity? I'm guessing time = O(n) and space = O(1). Is that right?

[theonlyme]

it's kinda funny how Nick is always High :D

[sanskargupta]

hello Sir
i am getting stuck at the below test case
[[0, 0, 0], [1, 0, 0]]
1
0
2

[zn]

just very curious why you need to write another function, is it possible that return it in the same function? I mean use the recursive for the function floodfill

[ruibinzhang]

The first line is essential; otherwise, the recursion function call will go into an infinite loop.

[harinijeyaraman]

Your videos are really helpful man ! Thanks a ton

[sanatgawade]

Can anyone explain why sc >= image[0].length and not sc >= image.length ?

[gillupenn]

Using same given function and not creating a separate method (I didn't feel the need)

public int[][] floodFill(int[][] image, int sr, int sc, int color) {
// find neighbours and add to stack
int val = image[sr][sc];
int left = sc-1 >= 0 ? image[sr][sc-1] : -1;
int right = sc+1 <= image[0].length-1? image[sr][sc+1] : -1;
int up = sr-1 >= 0 ? image[sr-1][sc] : -1;
int down = sr+1 <= image.length-1? image[sr+1][sc] : -1;

image[sr][sc] = color;
if (left == val && left != color) {
floodFill(image, sr, sc-1, color);
}
if (right == val && right != color) {
floodFill(image, sr, sc+1, color);
}
if (up == val && up != color) {
floodFill(image, sr-1, sc, color);
}
if (down == val && down != color) {
floodFill(image, sr+1, sc, color);
}

return image;
}

[richa]

we optimize this by not visiting nodes again which are already visited right?