Imagine there is a 5x5 grid of lights, and only the middle light in the grid is on.

The lights are wired such that when you flip the switch for one light (from on to off or off to on) the others right next to it (not diagonally) flip as well.

Using this weird wiring of lights, what is the fewest number of switch changes it takes to turn all the lights off, and which lights should you switch? (Assume all the switches work in the manner explained, and there is 1 switch for each of the lights.)

I'll try again ......,
This wierd wiring feature described in Gamer's puzzle made for some happy guys down at Tiger Electronics after the succes of their 'lights out' game a few years ago. I played it once in a toy store. It's quite frustrating.
I don't think you could set your own puzzle/starting position, but Gamer's put us in the spot of finding a solution if only the center light is lit at the outset.
Not all starting positions are possible - but the original game I believe only gives you possible 'winners' (I presume so that if you're stuck the computer can show off by solving it for you - smart a@$e).
The situation Gamer descrines is, of course, possible (as Charlie's shown) so I just thought I'd post this method of solving the real game (and quickly) so that you could show off to any annoying nephew who hands you his game. I take no credit for this method whatsoever. Please don't ask any questions as to how it might work. I don't know.
If you're going to practise this method go to one of the many 'lights out' emulators on the net. This puzzle is next to impossible to keep up with armed with your trusty pencil and paper.
Anyways,

Step 1
Remember, or have reference to this table

x---x............cc---
-x-x-............c--c-
xxx--............-c---
--xxx............---c-
x-xx-............----c
-xx-x............c----
xx-xx............--c--

x's are lit lights c's are 'clicks' and the .....are just to seperate.

Step 2
Starting from the top "Chase the lights down" this means switching the lights immediately below lit ones(to put them out).Start switching on row 2(to turn off the light in row 1)and carry on down until you hit row 5.

Step 3
If the puzzle is not solved look at the bottom row (the only one with any lights lit). Refer to the left hand portion of the above table to find the matching configuration of x's.

Step 4
Click on the corresponding c's in the top row (Row 1)

Step 5
"chase the lights down' again and this time
you'll get all the lights out.

With Gamer's problem we only need to chase the lights down from row 4 and we end up with a final configuration of
x---x
so now we click/switch on the first 2 in row 1,
cc---

which gives us a board layout thus,

--x--
xx---
-----
-----
x---x

chasing these lights down will knock them all out.
(note; you'll need a trusty pencil and paper to note which ones you've switched to answer Gamer's poser)
Hope someone finds this interesting. I'm a terrible typester and this has just taken ages.

Posted by Lee on 2003-11-02 23:32:30