8 queen problem
The eight queens problem is the problem of placing eight queens on an 8×8 chessboard such that none of them attack one another (no two are in the same row, column, or diagonal). More generally, the n queens problem places n queens on an n×n chessboard.
There are different solutions for the problem.
You can find detailed solutions at http://en.literateprograms.org/Eight_queens_puzzle_(C)