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 the row.

You can pause the showing or speed up / slow down the display.

If you select Find All, then all solutions are found - then press ShowSolns to see each of them.

If you select Find Unique, then only the unique solutions are found, that is those solutions which are mirror images are omitted. You can see each of them

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