3.7.156. n-queen

A constraint that can be used for modelling the n -queen problem. Place n queens on a 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 center of the chessboard so that they eliminate the maximum number of potential positions.