LeetCode 52. N-Queens II
Created at 2017-11-07 Updated at 2017-11-07 Category LeetCode
Follow up for N-Queens problem.
Now, instead outputting board configurations, return the total number of distinct solutions.
Same as N-Queens problem, it is a classical algorithm problem but it is not easy for newbies. To tackle this problem, we can go row by row, and in each position on each row, we can check if the current position is safe to place. So the rules are
- if there are no Queens in vertical and horizontal direction, it is safe
- if there are no Queens in 45 diagonal direction, it is safe
- if there are no Queens in 135 diagonal direction, it is safe
And if there are no positions safe to place a Queen, return to the previous row and move onward to choose a new position in that row.
And you can watch this video-N Queen Problem Using Backtracking Algorithm on YouTube to know more about N-Queen problems.
Note that in Python, if you want to deep copy a list, try
my_list[:] by slicing it.