Karthikeyan Madathil
2

It's easy to see that the answer cannot be more than 8 (since there are only 8 rows and columns on a chessboard).


It's less easy to see that the answer is exactly 8.  There are several possible solutions. One simple one is the "staircase" solution - verifiable as an existence proof.

Place queens on

  1. a4, b6, c8, d2
  2. h5, g3, f1, e7
Krishna
2

An official chessboard is an 8×8 board containing squares alternating in color.


We can't have more than 8, since you would have a row (and column) with more than one queen on it.

There are 12 unique solutions, plus an additional 80. See the image.

12 Possible casase



The 12 distinct solutions for n=8 are illustrated above, and the remaining 80 are generated by rotation and reflection.


Read more:

http://mathworld.wolfram.com/QueensProblem.html


https://en.wikipedia.org/wiki/Eight_queens_puzzle