3.7.164. n-queens

A constraint that can be used for modelling the n-queen problem. Place n queens on an n by n chessboard in such a way that no queen attacks another. Two queens attack each other if they are located on the same column, on the same row or on the same diagonal. A constructive method for arbitrary n>3 was first given in [FalkowskiSchmitz86]. An effective heuristics for the n-queen problem was given in  [Kale90]. It consists of starting to place the queens in the centre of the chessboard so that they eliminate the maximum number of potential positions.