N-Queens II - Leetcode 52 - Python

0:00 - Read the problem
1:40 - Drawing Explanation
8:45 - Coding Explanation

leetcode 52

#coding #interview #python
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[Hiroki-Takahashi]

Your observation of how to check the vacant positive/negative diagonal cells is brilliant

[stacysealkylee]

Just want to thank you for making these vidoes! You are awesome and helping a ton of people !!

[vasujain]

Appreciate the consistent vids. Also, this is just what I needed for the daily challenge! :P

[Raymond-Wu]

That nonlocal keyword was exactly what I was looking for! I had thought it was global. I ended up just creating the count upon initialization.

[李建宏-cy]

You make this problem super easy! Thanks!

[kasivisu]

Hi, I really like the way you describe the problem and solution. The conditions in the back track function should be or instead of and condition. Thanks a lot Man!!

[orellavie]

What is the difference between the queen 1 sol? It is exactly this one, besides counting instead of returning a one sol.
So the time complexity is the same approximately

[derpy]

We can ignore rows because of pigeonhole principle, each row must have a queen. If there are n - 1 rows and we have n queens then it is impossible to have a solution.

I think this is the best way to explain it

[oneepicsaxguy]

A lot of the times the board is identical if you rotate it by 180 degrees, which means you can cut the running time by almost half doing this optimization. This is easier to do when only number of possible orientations are asked, and I guess this is why this question is called n-queens 2.
Maybe you could make a video with the optimization later.

You can still do an optimization in the original n-queen but it is much much harder to do.

[ishanmamadapur]

How does the code identify different solutions, so when we use backtrack, we can come up with one working solution, how can we continue from the start after finding one working result?

[CS_nb]

Hey neetcode, do you think you could have a go at 1105 filling bookcase shelves? thanks

[melissac]

What would be a better way for Python(not python3) to deal with the non-local variable WITHOUT creating a list and returning the len(list)?

[youngtraveler]

N-Queens: The problem - HARD level => NeetCode: its a easy problem
N-Queens II: supposed to be harder that the first one => NeetCode: its easier than the first N-Queens

[chrisgalanis]

Hey, Great video. It was very helpful. Can I ask you what software do you use for the pen?

[itsrdb]

Hi there! absolutely love your explanations, could you please make an explanation video on 164 Maximum Gap which uses Radix/Bucket sort? Thank you

[mehvashkhan]

can someone please explain me that how would the res pointer increment each time as a solution is found as the pointer is written to be incremented only when r==n, so that must be only for once then right? please guide me through

[kanishkkala]

i copy pasted n-queens and returned len(res) and well it worked, hahah :)

[thesouthsidedev]

what app are you use for drawing over?

[benjaminkeene]

Hey hey! I think you reversed posDiag and negDiag set calculation. It doesn’t affect it as long as you keep it consistent (which you did). posDiag should be (r-c), such as 0-0, 1-1, 2-2, which all equal 0. negDiag should be (r+c), such as 3+0, 2+1, 1+2, which all equal 3.

[abhishaiwinston]

Could you please do "sudoku solver" next?