"Lights Switched" toggles the cell selected and its immediate orthogonal neighbours.
"Lights On Diagonally" does exactly the same except that diagonal neighbours are toggled on or off, ie, if a neighbour is on it is turned off.

Select an "N x N" grid size to display that grid for examination.

Offer a lowest switching sequence for each grid (for the 3 x 3 it takes 5).

(In reply to re: computer solution by brianjn)

yes; similar programming, except that evaluation of the "lights switched" had to await the final row, but on the other hand only the top row was arbitrary and had to have every choice taken, as opposed to also the first column in every row.

Posted by Charlie on 2009-07-16 01:15:48