N-Queens - Backtracking - Leetcode 51 - Python

0:00 - Read the problem
3:56 - Drawing Explanation
12:27 - Coding Explanation

leetcode 51

#backtracking #python
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[Cld]

Backtracking never been this easy after watching your video! Thanks for the excellent intuition about backtracking.

[wookyumkim]

I love so much the idea of using posDiag set and negDiag set. That is the truly brilliant trick.

[harishsn]

such an elegant and simple solution without having to pass through loads of different function unlike other videos I've seen. Thank you for this.

[arjunv]

Like the clear explanation of the problem and the code walkthrough. Please provide your analysis on the time/space complexity for each problem you are solving.

[salehsaeed]

I have been watching several videos on n-queen, your video is the most understandable

[rajrsa]

I had seen this problem for the first time about 7 years ago in uni and I was too scared to even attempt it.

Thanks for explaining it so beautifully and helping me conquer my fear. (I was so stupid to be scared of this problem lol)

[chaitu]

I was a bit confused by the problem statement, but your explanation made it looks as simple as possible. Thanks for making such amazing content.

[slygg]

Altough it's an understandable reflex to use a 2d-array to represent this chess board, since a normal chess board is a matrix, in this case that's subobtimal. Since the problem definition is so that you can have only one queen/row anyways you can just get away with a regular array<int>. When you do this checking for conflicts also becomes less computationally expensive since you can just do this: Let b equal chessBoard, if b[row] == b[i] || abs(b[i] - b[j]) == abs(i - j)), conflict found. This probably doesn't matter for small n but once n gets moderately large every little bit starts to add up, especially if your method is time complexity O(n!) as in the video here.

[umutkavakli]

I can't express how this explanation blew my mind! You're the best, thank you.

[jadkhalil]

Easily the best explanation on the internet thank you so much for your contributions :)

[symbol]

Awesome, I solved it by using a helper to iterate through the rows then columns, then diags each separately O(N) for each of those loops, but this way is much better.
Thanks man

[onlinealias]

I started doing this problem and it was tricky, but the first part of the vid set me on the right track to code it up myself. Thanks bro

[LeeK]

Brilliant solution; I learned a lot from the whole concept of (r+c) and (r-c); really great learning content.

[ramanpreetsingh]

Whenever I watch you solve a problem I feel that if coding was Earth you are Mt Everest and I am Mariana Trench. One of the best and easily explained explanation

[SameenIslam]

You explain difficult to understand concepts with amazing clarity, thank you for your work!

[DanielTruongDev]

For those who confused what's the purpose of backtrack(0) code, it's basically call the backtrack function starting at row 0

[vesicapiscis]

This is the best video on backtracking I've seen so far. It was so good that I applauded after watching it.

[Cakie-sogv]

In terms of the time complexity, don't forget cloning the memory of the board (n^2), except for it, I think the time complexity would be O(n*n!), cuz your tree has n layers, n! is just the number of the bottom level, so the total time complexity I think is O(n!*n + n!*n^2) = O(n!*n^2), that's why the bounce of n is pretty tiny (1 <= n <= 9)

[wessamyaacob]

AWESOME! The best channel every for explaining problem-solving questions and how to think about them, rather than just throwing the solutions in front of the audiences. ❤

[parthsalat]

Thanks for speaking clearly...was able to watch this on 2x