The Eight Queens Problem. A movie

This movie does not show the complete solution. Alice code doesn't run fast enough to show it all without an enormous file. It shows enough, however, to see the point at which backtracking begins.

Note that the speed is being manipulated as it plays, so that much of it runs at Alice's fastest normal speed.

When a queen is initially placed on a street, the robot checks to see if there is another queen (beeper) on the same avenue, and on the two diagonals. If there is, the position can be attacked, so the robot moves the beeper and checks again. When it finds no successful attacks it moves to the next row (street). However, if it tries every corner on that row unsuccessfully, it must back up (recursive backtracking) to the previous row and keep trying there. The program eventually finds a solution.