In the eight queens puzzle, you need to place eight queens on a chessboard so that they aren’t attacking eachother. It has 92 solutions.
I implemented one method for solving the problem. It works for any nxn chessboard, but it’s not so fast with large boards.
You can invoke this with java -jar Queens.jar for an 8×8 board, or java -jar Queens.jar n for an nxn board with n queens.
It works by processing the board in vertical strips, first placing a queen in the top-right, and then attempting to place a queen in the second column at the first available space. Once it crosses the board like this, it has found a solution, but it goes through plenty of bad combinations first.
Update: online solution-viewer is now running to make that command-line output more useful.