N Queens Problem

The puzzle - to put n Queens on an n*n chessboard so that none is in check.

You select the size of board and one solution is found. Press ShowMoves to see how it does it - using backtracking - where the program tries to place a queen in one row, and if successful tries to place one in the next. If it cant find a place in the next row the current place must be wrong, so the program looks further along this row.

You can select Find All solutions, then press ShowSolns to see them.

If you select Find Unique, then just the unique solutions are found (ignoring mirrored / rotated solutions)