# Many more Lights Out

##### July 17, 2010 mathematics

A very long while ago I posted some solutions to Lights Out; back then, I solved the -by- board by row-reducing an -by- matrix.

Since then, both Boris Okun and Brent Werness pointed out to me that I should’ve solved Lights Out by using a *scanning algorithm*: propagating the button presses down one row at a time, and exponentiating the propagation matrix to make sure that I don’t get stuck at the last row.

This is much faster.

With this method, here is a (scaled down, auto-leveled) 2000-by-2000 solution:

And here is a (very much scaled-down, auto-leveled) 5000-by-5000 solution: