Code Golf: Lights out

Answer 1

Ruby:

class Array
    def solve
        carry
        (0...(2**w)).each {|i|
            flip i
            return self if solved?
            flip i
        }
    end

    def flip(i)
        (0...w).each {|n|
            press n, 0 if i & (1 << n) != 0
        }
        carry
    end

    def solved?
        (0...h).each {|y|
            (0...w).each {|x|
                return false if self[y][x]
            }
        }
        true
    end

    def carry
        (0...h-1).each {|y|
            (0...w).each {|x|
                press x, y+1 if self[y][x]
            }
        }
    end

    def h() size end
    def w() self[0].size end

    def press x, y
        @presses = (0...h).map { [false] * w } if @presses == nil
        @presses[y][x] = !@presses[y][x]

        inv x, y
        if y>0 then inv x, y-1 end
        if y0 then inv x-1, y end
        if x